It's something of a fallacy that only 'decent' people will be on paid sites.
There are plenty of weirdos (of both sexes) on both the free and the paid sites.
TBH it's a process of trial and error. All the men I have encountered via POF (with possibly 1 exception) have been vanishers, timewasters, married - but pretending to be single, perverts, sex-obsessed nutters, unattractive, unintelligent, misogynistic, racist, sexist, homophobic....I could go on but you get the picture.
OKC is a haven for the polyamorous, fetishists etc. I never even got a message worth replying to!
MSF is terrible, very low traffic and most people aren't subscribed.
Eharmony is even worse. Run by Christians and won't let anyone spearated but not divorced be a member
. Also they pick your matches for you, and there's something weird about the photos, can't remember what exactly but I think you can't see people's photos unless you're a mutual match or something (I never joined but have heard several people say this in the past)
Sites like GSM are good if you're a) in a big city, or near to one and c) are a middle class guardian reader. Or look like you are.
I have heard good reports about Lovestruck, but I believe it's only in London. And again I suspect a little bit middle class and earnest.
I'm going to say Match is the best because that's where I met the lovely man I am dating :) One good thing about it is that they often do 3 day free trials, which are worth a try.