This is the classic "different strokes for different folks".
Having said that, IMO, SPs and real life dating are at the opposite ends of the spectrum. You choose either pricey convenience or time consuming but free (at least to start). The 2 endeavors are completely different and can never be confused with one another. This makes my life simpler, and it's greatly appreciated.
SA, however, straddles and blurs the line between the two. It's elastic, as in it can veer towards one end or the other, depending on your arrangement with each individual SB. Some ppl prefer this, as it offers flexibility. Others find it too complicated and time consuming. Both views have its points. I lean towards the latter.
It comes down to what you are looking for. Just Sex? Romance? A bit of both?
If it's just sex, then surely SP is the simplest way to go. There's something to be said about keeping life as simple as possible (for those who say it's cheaper to find those rare SBs who charge less but are just as good; well, power to you. For me, all the time that's needed to search & find those gems, plus the disclosure of personal info are just not worth it.
If it's for romance, then SPs are definitely the wrong place to look. On SA, unlike in real life, you are still only meeting girls who've been "pre-screened" to have indicated that they're willing to trade sex for money, at least in some capacity. Their #1 motive is still money, which isn't the best foundation for love, wouldn't you agree? Also, you are only seeing one segment of the dating pool, because not every eligible female will be on SA. You are missing out on all the others.
The 3rd option is the most intriguing. This is for guys who want it all. They want to play all the fields. Probably see SPs, as well as SBs, maybe dating in real life too. If you are one of them, god bless you. You clearly are operating on a higher plane than me. I can barely manage to keep one lady happy at any one moment.
As I mentioned before, I greatly appreciate the simplicity of SPs. Life is complicated as it is. They provide a welcome break now and then. When I look at SA, my number one reaction is always "careful what you wish for".