hmmmm........
depends on wood.
i'm fundamentally a lazy person. so, i run skip chain so that when i hit a rock it takes less time to sharpen.
and, i run a 28 inch bar so i don't have to bend over as much, and it mounts better on the processor.
also, both my 7900's have been woods ported and fiddled with.
cutting up to 30 inch green white fir, it cuts a little faster with an 8 tooth sprocket then 7 tooth.
smaller stuff the 8 tooth still seems faster.
also, depends on how good you are at sharpening. it seems like the better i get at sharpening, the faster the 7 tooth gets compared to the 8 tooth.
a guy who knows more then me insists the 7 tooth is faster then an 8 tooth usually in this class of saws, but he also cuts harder wood then me.
pretty cheap to try though.