We slept in a murphy bed for 5+ years. This murphy bed cabinet was 10K (purchased by my ex, a story in itself), but the actual bed mechanism was not that expensive. Murphy bed is as comfortable as the mattress you buy. On the other hand, sofa bed is as comfortable as the mechanism (a lot of firm support), and the mattress also needs to be thick enough. The only sofa bed I ever liked was made by Carlyle Sofa in NYC.
As I get older, I need very comfortable bed, otherwise I get backache and such. I don’t think I would make a sofa bed my permanent bed. My kids will not sleep in a sofa bed at hotels. They insist on having roll away beds instead.