I've used em both and couldn't tell a difference. From what i've heard though- if people do have a preference it seems to be for the BDs... some claim they're sharper.
Terumo all the way - I seldom feel the needle going in. With BD, I always feel it more (a little pinch or twinge). Just think the tips are not cut the same way as Terumo; not just an issue of sharpness but also shape of the needle so that it eases into the tissue with minimal pressure.
I prefer the B-D. The have the larger "grip" flaps at the top for better stablization and handling. The Luer lock also slides on easier and the needles are never bent, whereas with Terumo some of the 1.5 inchers are slightly bent which can make for an un-even entry into the muscle.