If you want to become a better driver 2wd is the go. You have to learn how to use less traction. It's cheaper too, less tyre wear.
More rewarding for me. Though stock can become expensive to ensure you have a decent motor. I'm not at the front but I also want to know I have the same grunt as the fast guys. I use a schuurspeed v3 which is just as fast as everyone else (down the straights at least) My Tekin redline gen3 is great in my 4wd stock as well. There are other popular fast motors too. Trinity, team powers, etc...
Importantly, think about the car you will love to drive. Make sure whatever you choose keeps calling you back for more.