On average MILFs provides the best service. Many of the younger ones thinks they are 'all that ' (so to speak) ; With the exception of a few.
The best ladies I have had experiences with were actually a little older and all were already mothers.
Age range is 30-40, but I will go to 45 for Asian providers. It's not only GPS with the younger ones, they just haven't acquired the needed skills yet.
They do give the best sessions. I also agree with the exceptions of a few young girls that give a great session. I can attest to that because I'm currently seeing a young UTR girl that's in her 20's. She's totally awesome.
I'm slowly compiling a list of delicious p4p women of different age and ethnic backgrounds.
I really don't trust generalizations like the OP's.
I've always been one that needs to find out for myself. Hehehe!
Now back to the research lab.
Damn, how great is this!
... but in the escort (and stripclub) world the youngun's can definitely hold their own 
Since I am older, I just feel more comfortable and not a "dirty old man".
Once and a while I will play with a 20 year old, but I prefer the over 35 crowd.
And frankly prefer them due to age and similar life experience. In addition to getting off I enjoy this world when I get to know these beauties, albeit mostly naked, LOL!
I started when i was 25 (im 30 now) i didnt think i was "all that" i was just immature and didnt know what the fuck i was doing lol.
One more thing, what made me see the light was this (i worked for an agency at the time) the lady who ran it politely but firmly told me "these guys are paying your bills!" that quote stuck with me like white on rice and while im not a doormat for poor treatment, i never let myself forget that quote. It matured me quite fast.
You all suck. Give me a 25 year old hottie, true to her age, of course, and I’ll feel like a king in my castle. No need for her to perform. It’s good to be the king, at least for an hour.