Would you like to do 3D or pattern style aerobatics? there are many types of aerobatic airplanes and your choice will be limited to which style you want. If you are just looking to get your feet wet, you can look at the baby blender, spitfire, mustang or HotWax's ugly stick. I would personally recommend the spitfire as a first aerobatic airplane because of how floaty it is. The baby blender is a great plane, but it does not really like the wind and NEEDS as 2200MaH to fly well. Any of these would make pretty good pattern style planes, but of you are looking at 3d I would try the twisted hobbys crack yak. The thing is the closest to an indestructible aerobatic plane that you could possible find, and it will grow with you. It can do pretty much any maneuver you throw at it and the 10mm EPP just absorbs a hard hit. Although I've not flown mine yet, the 3D hobby Shop slick 42" can do both pattern and 3D depending on the throw you give it. Aerobatics is one of the most fun (in my opinion) things that you can do in this hobby and I love flying scale and 3d aerobatics.
I would have to agree with AkimboGlueGuns on this and a real good plane for your first prob should be the spit. It has larger control surfaces that can help pull off some pretty rad tricks. Clip the wings and youll have one hell of a roll rate. But you have so much to choose from when it comes to acrobatic capabilities. It just depends on what kind you are looking for.
Now if you are looking for an advanced aerobatic airplane to train on I would defenitly go with the parkzone extra 300( that is if you have a decent amount of 4ch experience). This plane is absolutely phenomenal! I love mine and have a blast with it! But If you are just looking for a 4ch aircraft that can also do a little bit of aerobatics I would go with the parkzone t-28 or parkzone artisan. I have flown the t-28 and it is a fantastic trainer for 4ch flight and even aerobatics. I havent flown the artisan but I have heard it is just as good as the t-28. Have fun and fly safe!
If you want something fun and snappy, go for a UMX Pitts. I know its tiny, but you can do crazy stuff with it. I have one and it flies AMAZINGLY. It rolls VERY crisply, and has AS3X which really helps stabilize it in winds. It doesn't like to hover, but has plenty of power.
2. Straight long lines
3. Long rolls
4. Multi-point rolls
Not very good at:
2. Torque rolling
3. Something I don't know the name of (Rolling fast above the ground, but keeping it level and steering).
4. Landing (It comes down fine, but just is kinda unstable on the ground in a wired way)
5. Gliding (Its a biplane...)
The AS3Xtra is good because it's really inexpensive. I have it and I love it. If you're learning to fly 3D, you can lower the throws on the servos, and its a lot easier. As you get better, raise the throws and you can do some hardcore 3D!!
The FT 3D is awesome and the Racer, though a bit fast for a beginner is also. My vote would be for the FT Bloody Wonder. Very aerobatic, controllable, can be flown slow, and extremely easy to build and repair.