I'm 230lbs and had similar concerns. Flow recommended either the NXT-FSE or NXT-NRX. I ordered the FSE which is slightly lighter and not quite as strong as the NRX. The main reason I went with the NSE, it's not as stiff as the NRX, which I was told would work an Intermediate pretty bad. If I was you I'd probably go with the NRX.
Flow told me to stay away from the AT series because it uses a nylon highback that is not as rigid as the one used on FSE or NRX.
I chose Flow over Cinch because the plastic chassis didn't seem as logical as the forged aluminum used on the Flow NXT line-up, at least for a heavy guy. I was told Gnu makes a Cinch type binding that uses an alum base, but I didn't hear about it until I ordered my Flows, so no research was done on those.
My conclusion was that Flow is the most widely used rear-entry system and the number positive reviews speak for themselves. I should get my Flows today, so I have no comment other than research related.