I would choose Coral Reef just because we went to San Angel Inn last year, and I thought the food was disappointing. The , salsa, guacamole, and some drinks. I don't remember what I had as an entree, but I didn't eat most of it. chips tasted like Tostitos, and the salsa tasted like it was made from canned tomatoes. I am a chip snob--I don't need real food, just bring on the chips
On the bright side, I liked the ceviche appetizer and the atmosphere was wonderful (we sat right by the river across from the pyramid). Service was slow, but friendly.
I would go to San Angel Inn again, but with lowered expectations. From what I've heard about Coral Reef, I think it might be similar in the sense that it's about the atmosphere rather than the food.