Complicated question. It certainly would've been better financially, though honestly, the difference is "set for life" vs. "set for a long time", so I'm not certain it would make a material difference in my life now. Besides, I think it's fairly likely that even if I were set for life, I'd be doing something fairly similar to what I'm doing now. I think that in terms of lifestyle & personal goals during the 4-5 years I would've been at DropBox, I actually did better (I ended up folding up the startup I was working on and working for Google, and I had a relatively stress-free, enjoyable, lucrative, and personally fulfilling time at Google where I grew a lot as a person).
I do think that my reasons for not taking the job have been invalidated by future experience. My top reason was "I'm not going to leave my cofounder", and then he ended up leaving me 2 months later. My second reason was "Well, you've got a startup, I've got a startup, it is unclear which of us is actually going to succeed," and of course my startup was dead in 6 months while DropBox is now a $10B company. (Interestingly, I had a gut feeling at the time that I was turning down something important - I could tell Drew/Arash/Aston were crazy smart, and I really liked their product concept video.) But Drew actually told me "Honestly, if I were in your position - and I have been in your position - I wouldn't take the job" and he was right. The bargain we make as entrepreneurs is getting to call the shots, and the consequence of this is that sometimes we make the wrong call, and in a way it's not wrong after all because the whole point was making the call in the first place.
There's also the issue of whether DropBox would be a billion-dollar company at all if they'd hired me. I think my skillset actually duplicated Aston's to a fairly large extent, and we would've argued over technology choices (I would've pushed for Django, JQuery, and git over Pylons, Prototype.js, and Hg - the fact that these won in the wider webdev world is immaterial, just arguing over them would've cost precious time that a startup can't afford). Instead they hired some very talented MIT grads instead, and my understanding is that these engineers were responsible for things like reverse-engineering the Finder and writing the syncing algorithm that were what really contributed to DropBox's success.