Moved from General Cycling.
A lot of people ride mtbs because they tend to be (slightly) cheaper than a road bike, most claim they are more durable, or they like to hit the trails on the weekends and they don't have the room/finances for more than one bike.
-Comfort: Go for test rides, as everyone has their own definition of what that term is.
-Style: Beauty is in the eye of the beholder.
-Lightweight: Again, different people have different ideas of what that is. Some people have no issues with 30 lbs, while others think that anything over 25 is a boat anchor.