Most ballet schools have their own requirements for slippers, including whether they will be leather or canvas, split sole or full and pink, white or black. Comfort, then, for the soft slippers, is the most important factor.
Most students do *not* buy custom made pointe shoes. This is generally reserved for professional dancers. Some companies, like Gaynor Minden, offer a huge variety of stock sizes and styles so a dancer can usually pick the combination of features that best suits her individual foot. She will need to consider length, box size, vamp depth, heel height and a number of other factors. This is best done in consultation with her teacher, since fit is of prime importance in pointe shoes. Improperly fitted shoes can cause injury.