With all this in mind, go with the Raygun. I have the 2010-2011 Raygun (base in my avatar image) and I'm a mid-west rider, which has similar conditions to east coast. It's by far the best board I've ever had.
It's awesome because it literally performs just as well on all terrains. I've rode it on ice, slush, powder and park:
1.) The ice is good. It holds well without catching an edge on ice, and works really well on groomed slopes which is what it mostly is on this side of the U.S.. On the groomers, the Raygun gives you complete full control; you can make turns gradually or really quickly.
2.) Slush was really fun with this thing last year! I used to hate the stuff (and my friends still do), but with this board I just laugh and go. It is a bit more slippery, but really it just performs as well as it does on hard groomers.
3.) It floats effortlessly in powder; I don't even have to lean back to float like I did with my last board.
4.) As for the park, it performs well here too. I never caught an edge in the park with this board and I didn't even detune them. It's nice and flexible, but not too flexible, so it's park-friendly but still gives you a good amount of control.
The K2 Raygun has also won the Transworld Good Wood award twice: in 2011-2012 and now again for the 2012-2013 season. The Gnu Carbon Credit has won one Good Wood award.
The price is decent, too. You can get a K2 Raygun from last season from somewhere around $250 and get this season's for $360, whereas last season's Gnu Carbon Credit is about $400.
I'm 6'4" and wear size 13 boots. I have the 160cm Wide, even though 165-170cm would be a more appropriate length for me. Although it's about 10cm short for me, it still performs perfectly. I'd recommend a Wide for you, although I don't think it would be necessary if you have size 11 boots because the regular Raygun is already kind of wide. stand on it with your boots before you buy it if possible, otherwise contact K2 and ask them.
Definitely go with the Raygun. It won't just be another board, it will become your best friend!
Also, make sure you check out the Good Ride's review of the Raygun (K2 Raygun | The Good Ride
) and the Carbon Credit (Gnu Carbon Credit | The Good Ride
). On both, select the "In Depth" option to get a fully-detailed review. These guys are good because they have a completely neutral opinion on everything they review. (Same with me, so you can trust me!)
Hope that helps!