I don't know, those places always make me want to throw up. Or go on a murdering rampage.
Either way, I like to avoid it if I can
There's something about the crowds there that makes them even more stupid and revolting than at other places like the Pantheon, which is usually really bad as well (crowd-wise of course, I would never insult the second most perfect Roman building).
Travelling alone is the key there. If you travel together you will nearly always stand out as tourists.