The higher end flows have more exposed hardware which can come loose I call this maintenance because this is true for all bindings regardless of brand. The FRX cost the same as the FSE but is more orientated towards hard free riding while the FSE is billed as a all arounder. Unless your a really big and heavy guy or just have money to blow look at the M9 and M11 as well because the difference in ride is minute.
hope this helps I have three pairs of flows myself NXT AT, NXT ATSE, and M9 I would not ride anything else. there more comfortable than straps and so much quicker to get in and out of.
"We live and die on our edge's" Vance H.