In terms of the gear selection, there really is no difference between 9, 9 and 10. All of them give you more than enough gears to handle any terrain with reasonable jumps in ratio.
If you are looking at the latest models of groupset, then expedition-touring quality transmissions would be mid-upper range (105 or LX) which are 9 speed, so thats what you ride. You can use lower grade groupsets for touring which happen to be 8speed. Really dont sweat it, but get the highest grade you can afford.
If you happen upon a new-old stock bike, with 8 speed XTR or Campy Chorus components, then just enjoy the high quality and you wont miss the extra cog.