I think if you are new, and don't have an established set of preferences yet, high-end Flow bindings might be fine for you. I say that entirely based on comments people have made on threads I've read here - to be honest, there's a MUCH higher percentage of Flow-users in this forum than in the real world, so pro-Flow statements should be read with caution.
Personally, I thought they were the worst things I've ever had the misfortune to ride (getting "in" quick isn't great if the state of being "in" is a compromise), but it's possible that they were a lower end model. I'll have to ask my buddy - all I know is that Flow shouldn't make low end models that are crap - you want customers to be satisfied and move up, not be disgusted and move on.
If that's the case, then whether the binding is stiff or flexible, the shape of the highback, pretty much everything but strap comfort aren't going to matter to you either - you are just learning what things should feel like. You won't feel like you are losing anything - this will simply be what you become used to.
The GNU bindings were intriguing to me, a girl I ride with who has a Roxy connection rides bindings that are identical to the GNU girls line, and she loved them. She never had to mess with her toe piece, and they held like a 2-strap binding, unlike the Flows.
Unfortunately (for me - I'm more of a park-style rider, at a small resort with all groomed hills), these are all pretty stiff bindings.
You might check out those K2 Cinch CTX bindings though as another option. Someone here mentioned those were not too stiff, compared to the GNU lineup. I was concerned because the frame actuates to facilitate getting in and out, that it might not be quite as responsive if there was any slop that developed in that mechanism over time, but it's worth checking out. I've read lots of online reviews after seeing them in person to see how people felt about them, and most people were enthusiastically positive.
Unfortunately, there aren't many reviews on the GNU bindings.
The GNU bindings are clones of SP bindings - a brand sold in Australia (apparently at a huge premium) and possibly Europe.
If you search for reviews of those bindings, you'll find more reviews - also mostly enthusiastically positive.
And first, fundamentally - you want to determine what you want. Maybe a stiff binding IS what you want, for your kind of terrain and riding style.