IMHO. Corpus has the best wind and SPI has the best waves, although both spots are mostly wind swell. Corpus has a park called Mustang Island with warm showers and camping spots with electricity or you can steak out your spot on the beach. You can ride just outside your tent for miles. There are several great flat water spots within 30 minutes of Mustang. Look at www.kiteboarding.com
and where to ride. There won't be many people there that time a year, just a few fishermen. Hotels that time of year are very cheap. We stayed at a brand new Days Inn about 5 mi from Mustang last nov. It was $38 a night for 2 kings. A bunch of us from Dallas will be there for the Thanksgiving week again this year.
Spi. Have been there several times kiteboarding and not. The north flats is where most go to ride on the bay. It has always been a little gusty to me there cuz the SE wind comes across the island. The surf side is great. You can start in the park at the south end of the island and do a 15 mile downwinder on a South anything day. The surf is much cleaner and more organized than Corpus, at least in my experience. No experience with beach camping in SPI, but the hotels should be cheap there too.
Shops are right on the island in SPI, where they are in town in Corpus.
Hope this helps