A lot of providers use these services but a lot of them don't as well. Some will take them as part of screening but still request references.

However, they can be a big help to a newbie - just don't be surprised if it's not always enough. Which one you choose should depend on what providers in your area seem to prefer. Check your area ads and the service's listings for girls you might be interested in (they usually let you look at the listings even before you enroll - they just don't display details) and try to see which service seems more prevalent and/or has more ladies that take your fancy.

From what I understand the three services are fairly similar but I believe Datecheck offers a lifetime membership option while the others don't.

RS2k is mainly Chicago area, & is not widely used in other states/cities. P411 is my preferred, but I also accept date-check... I think P411 is the most widely used.