This is an interesting thread. I have no idea because the girl always brings the condom. I nver buy them. I can tell you, however, that I have felt differences. I wish I would have inquired as to the different condoms that the girls were using.
Also, I believe if I was the SP, I would research the condoms and find the most reliable brand. I would supply them so that I know the John is using the newest most reliable condoms on the market and not something that has been in a wallet for 6 months.
This is more critical for SP because she is putting her ass on the line 10-20 times a week while I am seeing 10-20 girls a year.