Duo Rs are no more reliable that original Duos. There is a sound problem with original Duos, but I've played the crap out of mine and never experienced the problem. All Duos have the same CDROM, so that's going to be the same reliability-wise. The Duo R is cooler looking, but honestly doesn't feel as quality when you're holding it. Its lighter from the fact that almost all the shielding is missing from the inside.
Buy a Duo R because they are cool, or as a spare, but don't expect it to outlast an original Duo.