Search "trackball high lip normal" and the top was
to here. And the ones down from that are pretty good too.

(edit: I searched the same words again, and the top few changed just five minutes after the first search

.)
The only difference between the normal and the GT TB is the top half of the case:

. So, yes the high lip is what "sets it apart", but not that much. I believe happs has switched all TBs to the new red boards, so both have the same spin speeds. The GT TB itself is not stronger or more rugged than the normal TB.
The mounting is a totally separate issue. Both TBs can use either the normal 3" mounting plate or the GT heavy duty, and visa versa, AKAIK. However, the GT mounting kit (aka "heavy duty mounting kit") is, surprise, more heavy duty. It's also bigger. Happs came out with it supposedly becuase the other mounting kit wasn't strong enough for repeated hits of the drunk in bars.
Since you're not buying directly from happs, will ponyboy swap the balls for you?