Crabapple is the best I have had. I have never made it but I have tasted it. Amazing. It seems that, much like grapes, the sourest most awful tasting fruit makes the very best wine. Crisp.
I have been scouring my area for someone with a crabapple tree ever since that taste, no luck yet. Apparently they don't grow them much in the South. But I'm still looking!
I could see using crabapples as an adjunct to other sweet apples for a blended wine or in primary. Personally, I have found that the sweeter the apples I have used to make wine, the more disappointing the end results. These wines can be raised by working on the back end of it all, but I still hold out hope for 50 pounds of crabapples on the front end sometime.
I'd recommend finding the sourest fruit you can get your hands on. You're gonna be surprised.