question about helmet blower

hey question for everyone out there

im running a top sportsman 1970 nova blown alky. im looking into putting a blower fan for my helmet to keep my visor from fogging up. ive already talked to a sales rep at f.a.s.t. about some info. now my question

do I set up the hoses to pull air from the outside, thinking that will be cooler than internal air?

or do I go with the fan pulling air from inside the car which will be warmer. I run zoomies so im not sure if the exhaust will get into me from pulling air from the side quarter window. any info or suggestions?