Well, the only leather available from the factory for the old cars was black, with red stitch on the seams. I'm not a big fan of black leather (gets too hot!!!), but I did want leather in my car at the time, so I went aftermarket. I was in New Hampshire at the time, and a lot of dealerships, for all sorts of marques, went through Classic Soft Trim for leather options. So it was aftermarket leather, but purchased through the dealer.
I opted for a really light grey color.
I personally think aftermarket's a better deal, and some say the quality's better. Depends on where you go though, and what grade of leather you use.
Personally? Had I to do it again, I wouldn't have gotten leather, at least right away. Why? The OEM seats aren't very good, and I really want sport seats. But not only are they expensive to get, but I have leather in my car, so I'd have to worry about matching the rest of my interior. (Maybe not right away, but eventually, if I wanted my car to look half decent.

)
To do that, I'd personally go with leather side bolsters and hip bolsters, and leather backing and headrest, but suede/Alcantara inserts (seat and back cushion). Leather's not grippy, as others have mentioned.
-S2-