Just remember that most of the higher end fillers are made for HIGH, HIGH quality finish, as in high gloss, finishes. They are made of finer materials not generally needed for prop work.
I just see so many people spend big money of expensive fillers, when some bondo and a can of high build filler primer will do the same job at half the price.
With most everything, it's a case by case basis.
And yes, stick with like materials.