As a more general statement, Brush On is generall for wall art sculptures (ex. a sculptur that hangs on a wall and has a flat back).
Rebound 25 is a Mold for things that are in the round. Every aspect of the things is going to be molded such as a helmet. Rebound is able to stretch more and still retain its detail.
Rebound 25 is almost always more acceptable. Adam used it for his ODST helmet And his Half cast AR.