I ran a single speed Langster through several winters (and summers) worth of road filth and bad weather.
12,000 miles, one drivetrain, two BBs and one pair of wheels.
Finally had to build some new wheels as the rims were paper thin and the hubs bearing races were on the way out, drivetrain would have survived a bit longer but replaced it anyway with the wheels.
I can see the benefit of discs but a few of my (maintenance shy) friends have had problems with stick pistons and seized calipers after a lot of winter filth. I'm not convinced in the long run whether the savings on rim wear are worth it, but the better stopping definitely is so given the choice It'd be SS Disc for me.
If you must have gears then I suggest something with an Alfine 8, much cheaper than a Rohloff, and more reliable than the gearier alfines.