Giving you an honest reply from my experiences.
Adult dating sites can provide some success. From my experience you'll work your ass off trying to pull something reasonable out of a sea of simply unattractive women.
A few times a year you will succeed only to find she is a head wrecker, but every now and again you'll find someone decent and bingo these are the girls we all want.
Unfortunately while there has been some good success stories for me over the years, in reality escorts are cheaper and easier.
If you spend the time in work that you will spend trying to find someone, you'll earn more money and get more sex with this money from escorts than you'll get from dating sites.
Also escorts don't call you, don't wreck your head. They can meet anytime and you don't need to book and pay for a hotel because they have their own place.
This said in honesty the sex is better with a "bit on the side" than with an escort, but it's a lot of extra work, a lot less flexible, and it's not cheap. (hotels, dinners, flowers, crap, birthday and Christmas presents and women always want to do something, it's not just about sex for them)