Questions in the form "who has better food Mexicali or __________" have the same answer -- always the non-Mexicali choice. I would go so far as to say that if you MUST eat at Mexicali, arrive an hour earlier than you planned and down four of their quite passable margaritas prior to ingesting a single gram of food. The food will still suck, but you won't care.
Well I can only report on one, but both times I have been to Mexicali I have been disappointed. One visit I had the carnitas which I found dry, and the second time I had a brunch dish--I forget the name but it was eggs over two cheese enchiladas, I ordered the eggs over easy they came out over hard, and the cheese enchiladas were a little much. But its always busy there so they must be doing something right, they do have good chips and salsa :)