Currently upgrading 5120D to 5163D: what to expect?

I’m obviously aware that upgrading will allow 16x writing on certified media, but are there more subtle improvements between the drive mechanisms? Are the burns on my staple diet of 8x media going to improve, for example?

Also, given a choice of blank media, is the 5163D generally happier with +r or -r? At the moment I’m using TYG-02 Taiyo Yuden.