I recommend against the highball - I got one and sort of wish I had the other. Haven't specifically tried the other, but the highball has some behaviors I don't like.
Specifically, if I am not careful to keep my hand flat and parallel to the panel surface, it is rather easy to cause the ball to jump up off its rollers and not register any movement. I can also put my fingers around it, and lift it in its socket fairly easily. The other thing is that it is quite a large bump on the surface of the panel, so whipping my hand over it really quickly is a bit uncomfortable.
It also veers to the left if I spin it straight up, no matter how I spin it. (even spinning it up and to the right, I see the mouse cursor in windows begin moving right, then reverse direction and end up in the top left corner.) This might be due to my slanted panel, or it might be something else. Don't feel like unscrewing it and playing with rotating it 90 degrees and remapping my optipac pins.
Anyone with a positive highball experience feel free to refute me and say why I might be having those issues though.