Same caliber between them. A machinegun must be able to put down some steel. Mag fed just isn’t going to do it in 5.56 NATO. If I had to choose, I’d keep the SAW, even with its problems. If the M27 was 7.62 NATO it would at least have a decent caliber.
Seems like a lot of lost time during magazine changes. Full auto is so you can send a lot of rounds down range quickly. Can’t do that if you are changing mags all the time. Might as well have stuck to the full auto M16’s.