My theory is based on the observation that while I've encountered many people who love Tigana, and many who love Lions of al-Rassan, a surprisingly small amount of people seems to love both. My theory is basically just that people love the one of the two that they read first, but then think the other one is an inferior and overly dramatic imitation.

Personally, I'm the other way around - Tigana blew me away, while Lions of al-Rassan seemed to waste most of its admittedly considerable potential. Among the many things irritating me in Lions, perhaps the biggest one was the assassination scene and its ludicrous aftermath. Seriously? Someone gets murdered and you decide to just play a game with your readers where they have to guess not even who the killer was, but who the victim was - could it be the big hero? Whew, no, it's not - perhaps this character then? Whew, no, not either. And so on down the list, until the anticlimactic conclusion. And then while I obviously don't mind that Kay deviates from the real history on which the book is based, I thought it was silly how the "Moors" (can't remember the in-book name) were driven out of al-Rassan entirely in the same generation, that didn't seem very realistic.