Funny, since the civvy 91's only came with the wide, everyone I know wanted the slim handguard. In green to boot!
Unless you had the bipod, then it made sense to have the wide.
But then I've never been a fan of fat handguards. I always liked the synthetic FAL hanguards, and think the MOE handguards combine the best feature of the FAL for the AR.
I never had an issue with the slim g3 handguard even with very hot barrel, but I shot irons so long I never curl my thumb & fingers around the forearm like the AR "push the barrel" fad has folks doing.