First off, this is in the wrong forum. For future reference, you may want to look to GT for a thread like this. No hate, just want to help a new member out.
Now down to business. Both binding are very good. The twisting heel on the FKS does indeed work and is a great idea. That being said, I believe the FKS weighs more than the Drivers but shouldn't be too much of an issue.
With Pow skis it is all personal preference and body type. I am 6' 2" weigh 155 and have a pair of 185 Line Mr. Pollard's opus. I was looking into skis over 190 cm but since I don't ski AK lines or charge hard, I decided that I wanted the Opus because even though they are 185, they ski like a 185; versus other pow skis that ski WWAAAYYY shorter than their length because the effective edge is a lot shorter and they are perfect for the type of skiing I do.
As for bindings, do you plan on touring? If so, do you plan on dropping cliffs, spinning or doing a lot of jumping? If that is the case, your choices are limited because many AT bindings (Dynafit, G3 etc.) Are not built for that kind of powder skiing. They are built for getting up efficiently and getting down quickly. If you are doing jumps, drops and spins, look at Dues, Barons and Fristichi's. Next year, Salomon is coming out with their own version of these bindings called the guardian. So is another company but I cannot remember who off the top of my head. Another REALLY cool idea is the MFD all time. This is a system where you can put your regular downhill binding on a metal plate; this then gets drilled into the ski and Viola! You have yourself a stable AT binding that will take all te Abuse of a Downhill binding.
If you don't plan on touring, than you would be getting a regular pair of bindings, which really gives you a shit ton of options.
Hope this helped
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