I prefer eharmony. Have used it for a while. They use a variety of factors to send you matches that are going to be, on average, more compatible with you, than you simply picking 10 search variables and searching randomly.
There can be quite a bit to using psychology and other factors (like one's primary and secondary "love language") to see if people are compatible. Also, since eHarmony is relatively more expensive than Match, people are (again, relatively) more serious about finding someone to spend the rest of their life with.
Obviously, nothing is fool-proof, and I have met a handful of truly crazy people on eHarmony. But will stay with them because, overall, my matches have been pretty good.
I also have a profile on a website centered around higher income/net worth people. As expected, most people on there are shallow, and just looking for someone with some bucks to spend on them and just be pretty arm candy. In addition to most of them not being cut from the same Live Below Your Means cloth as I am. There are a few rare hard-working people, but they're few and far between.