What is the actual difference between wafflecup and regular Skate line since there is no midsole?
The outsole is the main difference. Wafflecup uses a hybrid version of a cupsole/tread blended with their classic vulc sole/tread. Supposed to be a more supportive, yet still flexible nexus of cup & vulc.
More thorough explanation:
Skate Classic vulcs: standard Vans rubber compound sole - optimized for skateboarding (stickier rubber, deeper tread, etc) and a thick rubber vulc wrap. Internal shank is present in the rear/midfoot section of all the Skate Classics models i believe for improved stability
Skate Wafflecup: a hybrid of Skate Classic vulc in the toe/forefoot with a cupsole-like rear/heel section. No internal shank present. There may be some midsole in the rear portion, but I'm not positive without exhausting additional research. The texture on the vulc (toe area) is different than the skate classic vulc wrap we're used to, as well.
To me, the wafflecups are the worst qualities of both Vans sole types that created a mediocre (to me) shoe. Do they skate great? Yes! Are they more supportive & durable than the vulcs? I don't completely think so, but some will feel they are! I've enjoyed KWalks & Crockett 2 lows in the past, but they wear out & got floppy quite fast :/