so you don't have boots yet? street size shoe means nothing. a properly fitted boot usually is a half to a size and a half smaller than your street shoes.
chances are you will end up in 9.5s, if you still end up at 10 or 10.5 maybe just look for shrinkage tech in the boot you buy.
get the '50! but the 52 is less than an inch longer also, not a dealbreaker i'd think.
This. I wear size 11's in normal shoes but my current boots are 9's and they fit perfect with super feet.