ORIGINAL: Charlie P.
If you can't disable the ACT on the Cub and still fly it (simulator doesn't count) you won't be ready to step up to a Somthin' Extra. I don't know anything about the HobbyZone Cub to know if that "auto-pilot" is bypassable.
Building a kit is always preferable to an ARF provided you have the time to invest. If you do take your time you can build a better plane than an ARF.
If you get rushed and hurried an ARF would probably be a better idea. With no tools and supplies to begin with ARFs are cheaper, but if you intend on pursuing the hobby and building now is the best time to start investing in tools and skills. The Somethin Extra is a very good first kit and a good second plane coming from an aileron equipped trainer.
Yes, it is disableable. That's good. The Cub weighs 1.5 lbs - thats bad. No offense, but a 1-1/2 lb foam model does not react like a six pound trainer. You may need a step between that and a Somthin' Extra. Maybe not. Just be aware that the flight controls will be similar but the response and "feel" will be different. And a hard bounce will be less forgiven.
What he said.
Ken