My opinion is, they both do the same thing. I don’t believe I’m better or faster with either one. I do notice I have more of a propensity to short stroke the flat trigger vs. the curved, when I’m working on speed. I “think” it is due to the fact the trigger sits further forward as opposed to the curved.
My first non-stock trigger was a Geissele SSA. The next was the SD-C and I haven’t looked back from there. There isn’t a difference between the two as far as specs but the feel of the SD-C is just different and I like it much more than the SSA. I like the feel of a flat face so much so that I even have flat faced triggers on my G19 and P320. I haven’t tried out the MBT yet but for the price compared to the SD-C I’m definitely going to have to.
After installing either SSA-E or SSA triggers in all of my rifles (only 5 so far), I opted for my latest addition to have a Geissele Super Tricon trigger installed. This trigger has kind of a hybrid curved/straight blade, otherwise it is identical to an SSA. The feel, however, is different and takes a little getting used to. But so far I really like it and continue to use it with future rifles.
I like 'em both and have no preference, as long as they’re Geisseles. I have a mix of SS-A, and SD-C’s. Both are predictable, dependable and bullet-proof. I like the flat bow for rapid, follow-up shots. It indexes your finger with the guard amazingly well. Both are a solid wall with a light switch break, and feel great. I like the extra bit of pull vs. an “E” for when the heart rate is up; I can get to stage 1 without a surprise bang, and I know the next bit of pull will print a hole in whatever the target happens to be.
I have both with an SSA and SD-C however I am going to try the flat bow in a class this weekend to give it a more thorough assessment. As it stands right now either one is fine with me and I really have no preference.