Wojo and I were comparing these at Daytona this year. I have the Triumph bars while Wojo just put on the Bellacorse bars. I'm kinda partial to the T bars myself.
T bars - upper and lower attachment points are on the frame of the bike, walls of the tubing are thicker than the B bars, smaller profile, their shape will not bend into the header if the bar folds backwards towards the engine (the B bars will).
B bars - upper attachment point is the horn bracket, lower attachment point are screws that go into the lower holes of the foot control bar, diameter of the tube is bigger than T bars but walls are thinner, larger profile than T bars and easier to attach highway pegs.
Like I said, I like the T bars better and here's why. I have crashed with them on (~25-30 mph left lowside into moist ground) and the bar folded towards the engine but did provide protection for the engine. After the crash I got some more of the same type and replaced them (bought cheap from another member). I like the slimmer look and don't want highway pegs so these were the natural choice for me. I also know how they fare in a low speed crash.
The B bars look decent enough and if you never crash they could be more useful than the T bars since they have a place to mount highway pegs.
