I think the plungers on the b-d are better. I think the part you actually push is wider and more firm than that of the thermo. I think the thermo pins might be a tad bit sharper. Just my opinion though.
BD are way better than terumo IMO. I have had terumo plungers not seal very well. All of the oil leaked past the plunger so you just lost some good stuff, and I hate to waste good gear. FUCK terumo. Later, Bigwil
I currently have both on hand and IMO they both do the job the same. I have no problems with either brand, flanges, barrel size, plunger, etc. But if I had to pick one, I'd use the Terumo. They are sharper and they go in like butter. The BD sometimes have a harder time breaking the skin.