I too have used both and the material appears to be constant. One advantage to the 24’ roll would be that you will have a longer run with fewer seams to matchup. I actually added the roadbed to my layout after the track was down and no slicing was necessary on the straight runs. Slicing the roadbed in half as recommended and where there was slight cupping on the curves...a little contact cement took care of the problem. I do have screws only holding the track in place and through the trackbed material. That has worked well for my application.
