If you're not going to do some group training, I'd go for MTB setup. Only in a training group ride you need tight gear spacing of road setup - for everything else MTB parts are cheaper, a bit less demanding on maintenance.

For commuting, after a while, you might just learn to like and appreciate fatter tyres and fenders. Rear rack to leave all the goodies off your back (tremendous change in comfort that way).

Or you could get a cheap mtb/hybrid with fenders for bad days, and get a nice road bike for hot nice weather (if your roads are of good quality, road bike IS a joy to ride).