Thought I might weigh in with my experience... This was several years ago on my 1987 Corvette coupe. It needed new weatherstripping when I bought it, and I sucked it up for a few years before replacing it. I was a college student and not overly flush with cash.
So when I did finally replace it, I wanted to go the economical route, my car wasn't a collectible or anything, so why not save some money on non-OEM stuff. I bought my weatherstripping from I think CorvetteCentral and one other Corvette vendor. I believe the weatherstripping was Soff-Seal and some other kind. There wasn't one company that had all the pieces IIRC. Anyway, so about $600 and I replaced basicallye every piece of weatherstripping on the car.
The new stuff seemed nicer because it was thick and firm and not all flimsy and wrinkly like the original. It installed well and looked nice, right up until I tried to put the top back on the car... It sat about a half-inch too high, though I ultimately was able to clamp it down. I figured it would squish over time and get easier. Then I tried to put the windows up. There was no way on earth that was going to happen... The stuff was just too thick and firm to work properly.
Long story short I returned all of it, was out the shipping costs, and bought all new OEM stuff along with new retainer brackets and screws (which I'd recommend to anyone else attempting to do this, it's much easier and not much more money). All the OEM stuff cost me about $1100, I believe. But it was worth the extra cost because when I installed it, everything worked.
If you had success with aftermarket stuff, then that's great. However, not everyone does.
