If I was starting from scratch, I would do a GT for the reasons mentioned. Just less to fuss with, dont need special mags or messing with feed lips.
If I had to choose between the BR/Dasher, I would do a BRA.
Fireform loads are accurate enought to shoot in matches. Run a 28" BRA around 2800-2850 and you should get 2500-3000 rounds on the barrel. Lapua makes brass which is always a plus.