which bag is better?

lol.....this forum doesn't get as much traffic as it used to. Be patient.

I prefer the ball shaped one better for the following reasons:
1 - you can play around with different angles and distances
2 - better for incorporating overhand punches
3 - You can also practice footwork around the bag
4 - the shape is also more conducive to different types of uppercuts and hooks than the wall bag.
5 - the wall mounted bag is less forgiving for different heights

They're both good for different reasons. But if you have to choose one, i'd say the ball shaped one provides more versatility - you can get more use out of it.

 

^^^^^this definitely.