The choice of these two restaurants, both of which offer South Indian vegetarian food, is as much a contrast of the catering the clientele type as it is how they prepare their dishes. In both locations we ordered far too much food to finish, and the main topic of food comparison will emerge from the pages of the Houston Press Eating Our Words blog. Instead, I'll focus on what was notable at either location.
Our large and raucous group certainly garnered attention at the quiet little Udipi Cafe, both because of our copious appetites and bizarre questions (BYOB? From the traditional vegetarian Hindu perspective, I don't think drinking wine at the table is ever a consideration. This was a double-whammy considering we had a sommelier dining with us). That aside, the food was, for the most part, fantastic. Sambar was spicy and ubiquitous (sadly, texturally identical as well) as glasses of water. Then again, we had to have curries, dosai, pullaus, and, heck, two full on thali dinners. Very few clunkers in this set (I'll count among them this odd yogurt cilantro drink. Probably an acquired taste.). The paneer curry here is perhaps the best implementation of paneer I have ever had. Rather than a crumbly or spongy affair, the paneer had a slightly chewy consistency akin to mozzarella, and the expert spicing worked very well with the texture and flavor of the homemade cheese. Eggplant curry was silky and bombastic, rava masala dosa crisp and crackly, the simple dish of cabbage and lentils sing, as does the impressively puffy (though greasy) battura. Get the chai if you can (the service is a bit spotty, perhaps due to the large group I was in) - it is redolent with cardamom, and thankfully arrives unsweetened for the individual drinker to adjust to taste. Too often chai is served far too sweet for my liking.
In contrast, the ITL Madras Pavilion actually has a wine and beer menu, is a certified kosher restaurant, and staffed by amusing and personable waiters who entertain their often not quite desi clientele (even in malleable crowds) with aplomb. The menu has cleverly designed a set Indian food dinner, which acts as a tour of South Indian cuisine shrouded in Western dining conventions. This includes miniature masala dosai (which is served with an absolutely stellar coconut chutney), some really nice croquettes, and a good selection of curries (saag paneer, korma, and chana dahl), and a really flavorful rice pullaw. It's a beautiful, "safe" meal, which didn't have the wild highs and lows of the OTL Udipi Cafe.
Which is probably just fine for the conservative diners ITL, and the adventurers willing to travel OTL.