With me personally, I have always needed Ariats that are half a size smaller than what I would usually wear, but everybody is different so it's hard to be sure.
I mainly wear the Coniston style, and with all this mud I always hose mine off before leaving the yard, I stay with dry socks providing I don't squirt the water into the zip so I find they're pretty good.
You've already ordered so it's academic now... but I find them very comfortable and completely waterproof. My only slight grumble is that for riding they are a bit lower and wider than the other Ariats like the Grasmere or Coniston, so I do find the inside of my leg is rubbed a little. But that's just the style of boot and they are perfectly fine for hacking and pootling about.
I think they are slightly generous on size so you should be ok.