So much attention is directed towards why "SBs" aren't "escorts."
My perspective is a bit non-traditional, because I worked as an escort, am pretty much who I am regardless or who I'm with, and have not had the misfortune of wasting 3-500 on an apathetic/bait-and-switch/dead-fish of an escort. As a result, I'm not really sure what differentiates an SB from an escort.
However, I can definitively say what a client will not do/does not do. (Or...well...clients sometimes do this, but if they do, they're out of the 'client' category and have become sugar daddies)
A client will not:
-let you crash for a week at his hotel room/apartment because it's peaceful/tidy and has an amazing espresso-gizmo thing.
-clean your apartment & wash your dishes while you're writing an essay/news piece.
-listen to you freak out about an essay/news-piece and help you write an outline.
-go grocery/bedding/cleaning-supply shopping with you.
-continue to see you if you show up (for a p4p type thing) & say, 'you know, I'm not really in the mood. Could we just cuddle and watch television?'
-give you a large sum of cash (without having seen you a few times) without the implicit expectation that you'll get down to business with each-other.
So - I guess the main difference is:
A client does not want to hear your drama/emotional issues - period.
An SD wants to hear about your drama/support you emotionally (well...as long as you aren't a drama queen) but doesn't want any drama/emotional issue talk that is related to him/a product of the relationship you have with him.
In platonic terms, a regular client is sort of like a colleague/class-friend/dorm-mate...in terms of the depth of interactions. An SD is like a BFF.