I prefer the fit of the Persols on my head. They seem to have stronger hinges and better construction than the RBs. By the time I retired my RBs (granted, after about 5 years of wearing), they were super stretched out to the point that they wobbled as I wore them. I had to take them to a optometrist to have them heat and mold the plastic frames so they would stay on my face. After about a year and a half of wear the Persols show no signs of wear and tear and the hinges are springy and firm.
I also prefer Persol polarized lenses to RB. While both are made by Luxottica, I swear that Persols have a far superior lens quality, especially with polarized lenses. At the end of the day perceived lens quality has led me to Persol. Even if there is no real difference, I feel a difference when I wear them, so that's all that matters to me.
I have the 2953 and the 714 and love them both. However, after trying them on I would highly suggest buying Persols off of eBay. I got both pairs for around $120-$150. The markups on glasses are ridiculous and there are several reputable sunglass dealers on the bay that come highly recommended. There are a few threads that name them, though I can't remember which ones.