I haven't had that much experience with custom iems either and I'm pretty sure that there arent many that have loads of customs/universal iems to compare but I did try the triple universal vs triple fi remolded customs. I preferred the universal fit.
The problem with my "test" was that the triple fis were meant to be universals. iirc, someone on head-fi talked to Jerry Harvey, who designed the tf-10s, told the guy that the triple fis would sound worse as customs since they were designed to be universal fit. This would probably be the case from going from custom iems to fake universal fit iems.