Actually you don't have to choose that. You can enable sync in Opera (stable) by enabling the sync flag:
opera://flags/#synch
And you can fix the find problem in the developer version too:
http://ruario.ghost.io/2014/12/19/workaround-opera-developer-28-find-in-page-crash/
What you have to choose now, is which browser you want to use; developer or stable
Yes! Amazing, thanks!