I have a really old Marin SS conversion. I'm a casual rider - 15 to 25 mile road rides with my wife around Austin as she does triathlon training. I have never ridden a Track Bike type SS, but I'm thinking about getting one. Here's the question to those of you who have both types: Which do you usually grab for a casual ride?
I have a frame which is basically a rigid mountain bike converted to single speed, and a track frame and I never use the MTB frame except in the winter when I need the clearance for larger studded tires. My riding is in the city and all of it is on pavement though, so that's what matches my needs. If you rode on gravel or some trails during the course of your day, the MTB would make far more sense.