The biggest benefit to a BT enabled powermeter is being able to update firmware or perform diagnostics with an app on your phone, instead of an ANT+ dongle on your PC. Stages are all BT enabled as far as I know.

As to the specifics of those particular powermeters, besides searching this forum you might want to check out DC Rainmaker's reviews.

Robert Chung will tell you, when buying a powermeter, to avoid low serial numbers. As a PM user since 2001 who has owned multiple different brands over the years, I fully concur with that. Apply that to your decision as appropriate.