I think that depends on how your body is. I have hips, am not necessarily the "fittest" person around, and had about a B size bra back whenever. I stuck with Underworks full tank binders (note I've only ever tried these and a tri-top from T-Kingdom).
Underworks:
I bought the 997 and then put the swim binder (I think 918) on top for both my everyday and swim wear.
The 997 rolled up at the bottom and created a "uniboob" effect on me, so the swim binder kept those two things from happening. My job required too much movement so the "tuck binder in pants" thing never worked for me.
As for the swim binder alone, it worked pretty well in the water the first few times I used it but seemed to stretch out/not bind as tightly faster than the 997 did. So again, I layered the two binders for swimming to counteract the looseness. If you feel comfortable enough, the swim binder looks enough like a normal swim shirt so you wouldn't necessarily have to wear a t-shirt with it. I personally preferred to wear a t-shirt over top of the binders while swimming.
T-Kingdom Tri-Top:
I didn't like it because I didn't like the material. It didn't feel "bind-y" enough to me, and I felt less secure. I also didn't like the fact that it wasn't a full binder because of the bra-like creases the ti-top appeared to have under a t-shirt. Again, this just might be me though.
I've heard good things about GC2B, but haven't been able to try them yet. Good luck, and do post back with feedback when you eventually decide/get one then.