Its a great question. I can compare my T5 Cali (owned for 7 years) with my T4 Bilbo Conversion (owned for 10 years before that). I looked at a really wide range of conversions before settling on the Bilbo. The quality of the Bilbo, matched or exceeded any of the others and the layout worked for us. I considered another Bilbo but found that the prices were not much less than the Cali. The Cali scored on spec and the brilliant integrated design, which no after-market conversion can match. After 7 years in the Cali, I can confidently say the quality of the build stands the test of time better than the Bilbo did.