Belt drive is proven to be very easy both on maintanance as well as driving forgiveness (GP or EP is the same thing).
If you play in parking lot, shaft might be a good choice since most of them using covered gear box (at least when standard
). Using front one ways is another problem for shaft driven car. Why, if one of the front wheel hit the board, it will try to break the shaft, if you change the shaft to harder material, other weaker connected parts including the gear, wheel axle, diff joint, etc will broke. So no matter which side is stronger, the other side will broke on impact. With belt drive, the belt tens to slipped from its pulley. This would be the point I said driving is more forgiving. Maintainning is the other easier area as most of the time you could clean those pulleys externally unlike if it were using the gear box that needs to be opened.
Shaft drive is always good for low end, it produce more torque with that particular tranny system but of course lack of top speed as someone mentioned here before. It also react to driver input faster and will give you more responsive kind of feeling.
Both some of the reasons below are still not answering your question because all car will be consider easy to drive if you set them up right. I meant, most car would have toe, camber, ride height, etc that could be changed. Plus make sure the have identical balance both R/L side, your car would perform as you like it. Only in theory, you wont get better balance out of the car that its fuel tanks is not center. But that only in locigal theory; the fact is still a lot of car without its tank center still enjoyed good handling. I guess around 80grams of constant unbalance weight does not do very much to the R/C car.
Hope simple explanation without those R/C slangs jargon explanation could enlighten your choice.