I would go for BACX. I joined Brymon on the Dash-8 & now fly the 145 when we were consumed by BA. The turbo props won't be around forever so you will end up on the jet. Better opportunities & less likely to be shafted if you go for a larger base - MAN, BHX, possibly BRS. Despite the whinging you read about here, I think our T&Cs are quite good, not the best, but OK, with many BA benefits, home most nights (I'm BRS based), salary OK as you don't have to live near London.
No experience of BM, so can't comment.