Robert, having used both types of knives in the wilderness around copious amounts of DEET, I've not had any problems with either. G-10 definitely holds up no problem. I'd need to spray down an FRN handle and leave it to be sure about whether or not it gets weakened by direct contact or not, but I've not had any real-world user problems with it.
DEET will literally melt and corrode many rubber, vinyl, and some leather into a gooey mess, but most knife manufacturers seem to be aware of the issues of outdoor knife use and have considered it in their selection of materials.
Hope this helps a little bit.