I don’t technically suffer from “premature” ejaculation — but I’m definitely interested in turning 10 minutes of lovin’ into 15-20!  I’d love feedback from those who have used Benzocaine or Lidocaine to do so on pros (and cons) of each, whether you think one works better than the other, and whether ultimately you felt like either made a noticeable difference. Thanks for your thoughts!

Or are you putting it on under your condum?

Condoms with benzocaine: they're a thing.  
http://www.condom-sizes.org/condoms/benzocaine-condoms-for-lasting-longer
http://nomorepe.com/how-do-benzocaine-condoms-work/
http://www.healthline.com/health/best-condoms-for-long-lasting
http://www.verywellhealth.com/best-condoms-4169709

My understanding is that you apply it 10 minutes or so before sex, let it absorb but then wipe yourself so there's nothing to really rub off.

Have you used them?  Do they do the job?  Any downsides?

http://nomorepe.com/how-do-benzocaine-condoms-work/
"... Benzocaine is a local anesthetic (a sodium channel blocker that inhibits the nerve signal outflow) and pain-reliever. It works by temporarily numbing and desensitizing the area to which it is applied. Benzocaine cream or solution ***inside the condom*** desensitizes the male sexual organ to help delay ejaculation and prolong erection during intimacy.
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"Condoms have a lubricant on the ***inner surface*** that contains benzocaine. This is why they look like normal condoms. You can’t tell the difference between a benzocaine condom or a normal condom by looking at them. You must refer to its label.
.
"How Do Benzocaine Condoms Work?
"Benzocaine is placed ***inside the condom.*** That is why something really great about these condoms is that ***your partner will never know if you are using a delay condom.***
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More details on the above linked website.

Numbing my dick means I'm not feeling the action really and that seems to me it would greatly reduce the enjoyment I experience. So I wonder if there's a bit of a quantity over quality trade-off going on here. If you try any of the suggestions give an update on if it going longer produced the same satisfaction as a shorter session where you could feel all the sensations.

Interesting point. But nothing turns me on more than turning a woman on, and my lasting longer will, hopefully, allow me to provide her with a bit more pleasure -- which will be more pleasurable to me.  So hoping that the "more enjoyment" will outweigh the slightly "less sensation." We'll see!