Gensher provides an interesting contrast to Nemmerle. Compared to Nemmerle, Gensher doesn't seem so nice. As an example of not being so nice, when Ged comes to him (after waking up from his coma), Gensher doesn't hide the fact that he thinks Ged is dangerous. (To be fair, Ged is dangerous: he just cast a spell that resulted in the death of the previous archmage. So, really, Gensher should thank Ged for giving him the opportunity for promotion.) Gensher also is pretty blunt when he points out how stupid Ged has been (4.78). To be fair, Ged has been pretty dumb, and Ged is sometimes hard to teach.
Gensher is from the island Way in East Reach, so he's probably black, like Vetch. This is pretty different from Nemmerle, since Nemmerle's associated with the color white. While, Nemmerle and Gensher are quite different, they both have things to teach Ged.