I'm no expert on this but the first thing everyone mentions is that a track frame's higher bb shell means that an x length seat tube will also be higher, in turn putting the top tube closer to your junk. This confused me when i tried out a track frame of the same length seat tube as my roadie and found it had less standover room. So if you plan on standing over your track bike a lot it's often recommended to get 2-4cm smaller size than your roadie.