The GT20 does have space for more tools but when doing a setup I find it less intuitive to visualize what tools will fit where so the setup takes longer than the TL2.
The turret indexes much faster on the GT20 and the rapids are much faster so when the one-off turns into 100-off they come off much faster.
With ingenuity it is possible to devise gang tooling on the TL2 and to some extent overcome the limited turret capacity.
However, it is also possible to do the same on the GT20 and you can sometimes leave more semi-standard tools in position with X offset ready to use.
The GT20 has a higher spindle speed and more power so it chews metal away faster. Although I recall a high speed (3500rpm) spindle option is available on the TL2.
The 12 inches of travel on the GT20 is a joke because you lose a few inches to the chuck. (This is something I find really stupid; the tool turret can overlap the chuck. Why? you are always going to have something in the chuck and a tool in the turret.) Functional Z travel is about 8 inches I think.
The GT20 is fiddly to work in and tightening a manual chuck is awkward, more awkward than the TL2.
It is possible to take the handwheels off the TL2, actually I removed the apron and that is where I attach the bracket for a coolant screen. (I am too limp wristed to use the handwheels; the jog wheel is much better for a decrepit old man like me.)
Get the TL2; for predominantly prototype work it is more convenient I think.