What type of riding will you be doing? If you're more into freestyle strictly then most people tend to go with a more flexible binding. That doesn't mean you have to get the binding with the most flex, because it really comes down to preference. If you're doing more all mtn riding and hitting up pow runs then you might want to go stiffer for better response.
Here's some more info on those.
The Five, Quattro and Quattro SE are in the H series
A lightly softer baseplate and hiback in the H Series makes for a mellow ride while still eliminating those bumps on the groomers, while Flow’s “Power-bridge” design gives you the stiffness and responsiveness you demand from a binding. The H Series is affordable, comfortable and reliable.
Flite 2 is in the Flite series
Flow’s Flite Series is for a more intermediate audience and will still hold up in even the toughest conditions with their injected DuPont Delrin (POM). For the soon-to-be-superstar, this binding series will stand up to most anything you can throw at it and is also flexible enough to lend your feet some much-needed comfort when you need it most.
And if that doesn't help you out much, just go over to the flow site and read up more on their technology for those bindings. And google some reviews. You should get more of an idea what's more suitable for your riding.
As for your sizing comment. The large flow binds can be used for boots in the 8 -11.5 So I think the XL's would be too big for you. Hoped this helped.
2012 Rome Postermania
2011 Flow NXT-AT's
2013 Flow Rival's