-R and +R are virtually identical for all common purposes. It used to be that most DVDROM drives loosely supported DVD+R, while -R functioned in any DVD player. These days, DVD-RW drives are so common that this is no longer the case. The +R standard calls for enhanced error control and extended support for Photo DVDs, neither of which the Wii will factor. So, it strictly comes down to what your drivechip supports more.
