OEM comes with a warranty
OEM comes with a "permanent", brick'n'mortar (dealership) location vs. ether/net/web/callroom
OEM costs more... for the above reasons
The dealer will sort out your van-type question. Prolly off-the-shelf available vs. ordering/waiting.
If you are cost-conscience, ask the dealer service advisor for a discount, you might be surprised at what they can come up with. Just remember that you can spend the rest of your life wondering "why didn't I just get it done at the dealership?" vs. "wow, I saved $100 ordering from the webnets"
...as you are standing on the side of the road.
Neither choice is perfect, but as my fabsaviour, Ray, always sez... "Wellll, Maaarc, the BEST just costs a litttle-bit moooore"
Caveat: My opinion is worth what you paid for it... I just experienced a rather scary dealership fail, (see "Near Miss and Broken Trust" on the forum) but at least I knew where to find the source of the problem, and I'm thinkin' that particular fail, from that particular mechanic is unlikely to happen for the rest of his career. Or mine. I'll be requesting him, specifically, next time I go in for service.
And there is always Gorilla Tape