There's no down side to epoxy primer. Self etching primer is a fancy way of saying sticky primer... and what good is a primer if it doesn't stick!?
Epoxy primer has the sole purpose of preventing rust; rust creep if scratched off and encapsulating any rust spores when applying it. If you want to risk rusting creeping under a scratch, then don't use epoxy primer.
Epoxy primer is very hard so it needs to be scuffed where you plan to paint it, just before you paint it. There's no substitute for epoxy primer, regardless of brand, they are all the same.
