What would adding wine (red or white?) do when cooking Vindaloo?
Ah, wine. "I love cooking with wine, sometimes I even add it to the food."

Anywho, your experiment shows that the short answer is "it'll probably come out quite nice". Most of these things have been said in the comments, but here's a recap:


Alcohol is a solvent, and so wine will presumably help eke out flavours from the spice solids to the liquid. (Much like you can make e.g. vanilla extract with vodka.)
Wine is also acidic, and acid is a general flavour enhancer (a bit like salt).
Wines contain varying amounts of residual sugar (ranging all the way from "almost nothing" to "syrup") which also is a flavour enhancer.
Vindaloo is based on a Portuguese dish prominently featuring white wine and garlic, so why shouldn't it work?


As for red wine, drinking a highly tannic wine with chili-hot food increases the perceived heat, but on the other hand, I can't say I ever really feel the tannins in cooked red wine and my experiences with using red wine in spicy food have been rather positive.