whenever a visitor comes to town, one of the standard recommendations is you have to go to frontera grill/topolobampo.
I can't speak for topolobampo, but i had the opportunity to have dinner at both frontera and the ixca again recently, and I 'd have to say that i far, far preferred ixcapuzalco.
why - the sauces. Not just the moles that bahena is famous for, but all of the sauces had a depth, richness and complexity that was lacking in anything we ate at frontera. Even the drizzling sauce for the fantastic ceviche was great. it seems at frontera now, that often the sauces relied upon are the bottled on that bayless pushes and while these are ok, they are made for the mass market, this had not been my impression the last time i visited there which i think was before the marketing/bottling campaign began
I also much preffered the service there, no 'tude whatsoever (which we did run into at frontera) as well as the huge tequila selection - and for this tequila neophyte a waiter who was able to recommend a couple different tequilas which pointed out the smoothness and differences of flavors available.
a while back there had been a discussion of ixca and it's overpricedness, and a few recommendations by rene of dishes there. The menu has changed somewhat since then but the standout dish for most every one at the table were the lamb chops in a deep, smoky,haunting red chile sauce that was literally wiped off the plate with anything handy. Also tasted were the carne asada, duck in almendro (sp?) sauce, quail in mole rojo, garlicky sea bass in banana leaf as well as numerous appetizers.
among the desserts theres a chocolate cake that's baked to order and the waitstaff will tell you it will take 15 minutes - it's worth the wait
in comparison to frontera, I found ixca in no way overpriced