while I never had the chance to compare a "squared/2" version of the 4B to anything else I did own/compare a 4B-SST to a 14B-SST and found that the largest difference in my system using the 1.6s that I had at the time were the details within the music that were present when listening at lower levels. While the larger amp was able to convey better bass at louder levels my "ah ha" moments comparing these 2 amps occurred when listening at lower levels.
Acquiring the latest and greatest albeit smaller amp would be nice and provide you with the most up to date sonic presentation that Bryston offers.
Many would say that the 14B would be overkill with the 1.6s but having the extra juice for a potential future speaker choice (like maybe 3.6s/3.7s

) wouldn't hurt, not that a 4B-SST2 won't do a great job with the larger Maggies.
As is always the case YMMV - good luck with your decision.