Better?
Fillers are almost always no mixing. Epoxy, you mix, then mix in microballoons, then try to get it on before it kicks. If better = easier, there ain't no contest.

On the other hand, if you're trying to fill a large gap the epoxy/microballoons can do it and won't crack or fall out later.

Filler loses the contest if the holes are much larger than pinholes. But it is going to be lighter. Trying to mix epoxy/mb to match filler's lightness is really difficult.