On the 'fake/scam' dating sites - you know which they are (hint: most of them don't even offer revshare as an option!) you should only go with PPS. Their model is convert the surfer as quick as possible and suck enough cash from him right away then who cares if he's not retained.
On the more traditional, community/real member dating sites, Revshare is your best bet. Often the program sets their PPS payout below what they know they earn on the average member (since they know how long he rebills) so if you assume they set 50% as their PPS offering then if you get 60 or 70% Revshare it will earn you more.
Then there is the fact of PPS promos though and the idea of getting your cash quicker (which you could re-invest into more traffic/marketing) to consider.
Lastly some programs have shady practices where they might not pay your remaining rebills if you choose to stop promoting them or at least won't make i t easy to get paid on them (one famous program in particular).
Thus ultimately, unless you get 70%+ Revshare from a company you trust, you are probably better off with PPS these days
