Don't get rio, it's too easy and sucks. get either seasons or space, angry birds seasons has tons of content and angry birds space is a completely different experience.
Tbh, ignore the IAPs and get Space. It's much more fun than Rio. I got bored with Rio instantly, but Space gave new life to my AB love affair
Go with Angry Birds Space if you've played the other games in the series. Rio feels way too similar to the Seasons and the original game. Space really mixes things up and introduces some awesome elements. You'll only need to pay $0.99 more to unlock the last world in terms of iAPs.
Yep, I agree. I've only played the first AB and, quite honestly, never even came close to finish it as I got bored with it. Got AB Space for free and, while still not an avid AB fan, I like the gravitational twist in it.