The decision on whether to go for the SE/Ocean or the Beach can sometimes be difficult and in the end only you can decide. However, having owned both versions at the same time, may I offer my observations to hopefully help you decide?
Firstly, forget any thoughts or suggestions that one version is better than the other. They are completely different vehicles and are designed to suit different life styles. We found both versions to be fabulous. We have since sold the SE simply due to our not being able to use it as often as we had originally intended. We will buy another when our circumstances change. So buy which ever suits your
long term needs.
I am not going to mention drive away awnings. An awning will of course increase the flexibility of both types of Cali but you must be able to use either version easily without one.
So the main reason for buying a campervan is to camp in and both versions do the camping thing very well indeed. So first:
Sleeping: Both versions have the same sized double beds upstairs. Once you have mastered getting up there you will find that it's not huge but more than big enough for two adults. The base is designed to have a bit of spring in it so you should find it reasonably comfortable. I suggest you get a Brandrup internal liner as this can make all the difference when the weather is cold, wet and windy. It also cuts down the light through the bellows on a bright morning. Both versions have beds downstairs that are easily put up. The SE/Ocean is obviously narrower than the one in the Beach due to the kitchen etc. We found the narrower bed to be comfortable but snug. The Beach downstairs bed is full width and very capacious. Both beds are quite firm and IMO both need the VW Comfort mattress to make them reasonably comfy, especially on the Beach due to the contoured bench seat it will have to sit on.
Cooking: You can cook in both versions. You obviously need to provide your own cooker with the Beach but unlike the SE/Ocean, that can also be used outside as well. Yes you may have to get out to get it from the boot but that will take no longer than it takes you to get out to turn the gas on with the SE/Ocean. Make sure you properly ventilate the van whilst using the cooker in both versions.
Fridge: The SE/Ocean has a very nice fitted fridge which appears to have only one main drawback. You have to take every thing off the lid to get inside. It doesn't sound much but it can end up being a bit of a pain. Again, you would have to provide your own self contained fridge/freezer for the Beach. We have a 12/24/240 volt self contained Waeco/Dometic fridge/freezer which is of roughly the same capacity and is brilliant. It is also portable so can also be removed into an awning whilst camping thereby freeing up more room in the van. These fridges are superb as they can be brought down to the correct running temperature and pre-loaded with goodies indoors prior to being loaded into the Cali and you decide where to store it, cabin or boot. They are designed to be used as either a fridge or a freezer. They also make a great foot stool.
Washing/washing up: You can do this in the small sink in the SE/Ocean. This vehicle also has both fresh and waste water tanks. We never used the sink as we found it too small. We also didn't get around to using the water tanks because we didn't use the sink, didn't want problems over the tanks and pipes freezing or issues regarding tank cleanliness. We just prefer to use water in separate bottles. Also, we almost always do washing/washing up at the site facilities which are usually more suitable. If not on site then we use our large collapsible washing up bowl. However, many other owners use all of these facilities in their Calis and don't find any issues so it's down to you to decide.
Storage: Basically the SE/Ocean has fixed storage facilities whereas the Beach requires you to provide your own solution. Personally, I found the fixed storage in the SE/Ocean to be very useful but some areas weren't that easy to use. The wardrobe is a very awkward space and we ended up using it to stuff bedding into. We never did find a use for the safe. We loved having the SE fully provisioned and ready to go at a moments notice. So it was perfect for us two old gits to go off and hide in. The Beach is a multi purpose vehicle so lends itself to a range of different storage solutions to suit those different uses. A quick weekend away will require a different storage plan to a longer holiday etc. This is where the flexibility of the Beach really counts. Nothing is fixed so everything is possible. It is very interesting seeing how owners have designed their own storage solutions. We use Really Useful Boxes which fit into the boot very neatly.
Comfort: The parking heater is essential if you plan to use your Cali all year round. It is standard on the SE/Ocean but an option on the Beach. Make sure you order one with the remote control. You can use this gem to pre-warm the van before you arrive back from a cold walk etc. You can also switch it on whilst lying in bed or having your breaky at home and by the time your get in it will be de-frosted and toasty warm.
You can make yourself very comfortable in both versions although you can stretch out a little more in the extra space provided in the Beach. With the front seats turned round both versions provide a cosy space to chat, eat, cook, read etc etc. However, you will find that the leg room is compromised if sitting in the swiveled front passenger seat in the SE/Ocean version as the kitchen unit is in the way. So you will have to sit at an oblique angle. Mind the seat doesn't mark your door card.
Seating to eat etc in the SE/Ocean is limited to four adults only (five in the Beach). However we have often used our seven seater Beach for picnics and have on occasions had seven seated round the table. When we've done this the two captains seats were occupied by little ones on the integral pop up child seats (option) but two adults could fit if the knew each other very well! We always remove the captains seats when going camping.
Reliability: If you intend to sell before the warrantee expires then this issue shouldn't worry you, however if you intend to keep your Cali long term then it's worth giving this a thought. The California is a very complex vehicle and with that complexity comes the inevitable problems. Many of the threads posted on this forum testify to the type of issues that can occur from time to time. So be prepaired to pay out to have issues fixed at some point in the future.
This is an area where the Beach does have a big advantage. Whilst you are able to do everything in a Beach that can be done in an SE/Ocean, the Beach doesn't have the same level of complexity thereby making it a potentially less problematic long term ownership proposition. The roof is manually operated with no complicated electrical control panel or electro/hydraulic gubbins to go wrong down the line. Just undo the security fittings and the two over centre catches and up it goes.
As you have to provide the self contained cooker and fridge/freezer in the Beach there is no gas supply system, water tanks, pump, valves, pipework, sink, tap, cooker, fridge etc to go wrong at a later date. If your self contained camping equipment goes wrong, it will always be far cheaper to either repair it or chuck it away and buy new than paying garage rates.
So the choice should really be dictated by your long term needs. The SE/Ocean is a superbly built polished self contained camper van suitable for up to four adults, that can and often are used as daily drivers. You can even have a Thetford 335 chemical toilet that fits under the sink

. We had one in our SE but vowed that hell would have to freeze over before we would ever stoop to use it. It was only there as a very last resort. We still have it mint and boxed.
I haven't mentioned the possibility of the fifth swivel captains seat option in the SE/Ocean as IMO it compromises the main use of the vehicle too much to make it a worth while option.
On the other hand, the Beach is a sort of Swiss Army Knife, multi purpose vehicle. If your family is growing and you foresee the need to transport more that four adults or have growing littleuns then I would suggest the Beach is where you should spend you money. These vehicles can be re-configured to perform many different roles e.g we have used ours as a seven seater people carrier for a wedding party, moved the bench seat fully forward to transport a go kart for our grandson, used it for picnics, a mobile beach hut, a sports pavilion that can be positioned in the best viewing spot, had regular massive dumps in (at the council tip) and had many gloriously comfortable nights away camping.
Finally, I have read some saying " by the time you've specced up the Beach to a resonable level the price difference is not that much so you might as well have the SE/Ocean". This is utter nonsense. You must choose the vehicle that's right for you. Price comparisons are not helpful.
What ever you decide, good luck and happy adventures.