window seals, aftermarket or OEM?

[WANT '71 280SEL]

(1979 300SD) I have recently had my windshield seal reaplced, and it still leaks. Not nearly as bad as it use to. I know it's not related to the body, becasue the water is coming in between the seal and the window. In particularly in the LL corner, and just a bit on the LR. I took it back and it seems they put some sealant in there, but it still is leaking. On the inside of the car I can see a gap on the inside of the windshield where the water is building up in. I can feel the gap with my fingers when I reach across the dash. Anyways, I bought it off and internet vendor on ebay, it was an aftermarket seal of course. Well, I need to replace my rear windshiell seal and I didn't know if I should buy an aftermarket one off ebay, adist, or cough up the money for the dealer. I will not do this myself, but will have it done professionally.
Thanks
David