I'm not sure that this question really makes sense in terms of modern evolutionary theory, because the term "evolutionary advantage" does not have an
explicit meaning. If I may, I would like to rephrase this question as
"Is being domesticated adaptive?" The meaning of the term
adaptive is actually somewhat
controversial among evolutionary biologists, but for this w/u I think it will be sufficient to say that something is
adaptive if, relative to other possibilities, the trait of interest has a higher
fitness.
Recall that fitness is defined as the number of descendents in a future generation of a population.
Given this understanding, we can ask if being domesticated is adaptive. We can compare the fitness of a domesticated individual to a non-domesticated individual. But the problem that we are going to run into right away is that these two individuals, the domesticated and the non-domesticated, are parts of two essentially independent populations, at least for most domestic species. So for your cats, the descendants of the domestic individuals constitute all of the future generations. Since they are part of two different populations, it really doesn't make sense to compare the fitnesses of the two groups. And since we can't compare the fitnesses, we can't say if one is more adaptive than the other.
In essence, I think that being domesticated is really more of an event than a trait. This question is sort of similar to asking "Was landing on the Galapagos Islands by the ancestor of Darwin's finches adaptive?" The event is not adaptive- it simply happened, even if it caused the great adaptive radiation of Darwin's finches we see today. If the ancestor of Darwin's finches had some trait which predisposed it to find those islands, than that trait might have been adaptive; the event was not. Similarly, traits which make organisms domesticatable might be adaptive. (I need to think more about this.) But the act itself is not something that can have adaptive value.
Is this what was originally intent by the question? I'm not sure it was, and I think it comes from a different intent of "evolutionary advantage." Evolution (as understood by evolutionary biologists) does not claim to tell us anything about the "point of life". We can't appeal to it for a justification of what is or isn't right.