It seems that I'm in a dwindling minority, but I think the food at San Angel is better than what's offered at La Hacienda. I find the menu to be more imaginitive and the flavors to be bolder and more balanced, on the whole. La Hacienda is nice, and the lakeside dining is location is fun, but the food is too, I don't know, normal for my tastes at those prices. Nothing on the menu would seem out of place at an On the Border. It's a better executed product, of course, but it's nothing exciting. I get that at San Angel. I just find the food to be more appealing. I'd compare it favorably with its sister restaurant in Disneyland, the Blue Bayou. Actually, I think I like San Angel better than that one, too.
Disclaimer: I haven't eaten at San Angel in over a year, and I do think it's a better lunch option than dinner option, provided that you're not there during Food & Wine.