My 09 Reliks fit pretty true to length, just a little wide, so you would probably want to go with a 10. That being said, if 10s are the wrong size, worst case scenario they are an easy size to re-sell.
I have a 9.5 and purchased both a 9 and 10 ronix bindings. The 10 was okay but the 9 fit A LOT better once it packed out. Initially my toes had just a hint of curl, but after 1 or 2 sets they fit like a glove.
IF you do find yourself with more room than you would like (before or after breaking in the boots) you could try wearing socks and/or adding in a gel orthotic to squeeze things up a bit. its easier to add than take away, but that is my opinion of closed toe boots based on using my slingshot boot. it has made it nice when sharing with my friends too. we all range between 10, 10.5, and 11. using a size 11 boot and the optional docscholes insert