Hi TT,
Cooter has given you a pretty good outline. I would only question his second paragraph. I also don't understand his reasoning. Both styles push the work down against the table, assuming the belt sander has a table and is set up vertically. I bought a 10" disk sander for the sole purpose of fitting pads and didn't like it as well as my 6" belt sander. I have also installed lots of them using a 1" belt before the larger one came my way. I sold the disk sander because it didn't work better for me and the disks were a pain to replace.
Either style will certainly get the job done for you. I like the B-square jig as sold by Brownells. I've been using one for more than 30 years. Instructions are included.
