I never noticed lag, even with full Sense and bloatware. I have a rom now with sense stripped out since I use LaucherPro anyways, and it flies. I forgot to mention earlier that I also leave my syncing on, Plume syncs every 10 minutes, my 2 Gmail accounts are instant, and Pulse news syncs every hour. I would say I use the phone heavily and it's more than stood up to the challenge. The only lag I've seen in person are with people trying that SPB 3D launcher, but that also looks like it might not be properly optimized code (just speculating based on the random lag spikes and my experience programming).
I would pick the Tbolt over the Dinc2, but it depends primarily on the size you prefer. I wouldn't choose the Charge over the Tbolt, mainly because it's a Samsung with almost identical specs.
Let me know if you have any more questions.