I have the feeling that the people who voted chell weren't thinking logically, and only voted for what game they liked more *cough*And they probably played the console version*cough*
Faith would win, without a doubt. Faith could get close and disarm Chell, or shoot her at a distance. Chells location would be very predictable because, ya know, Portals... And the Portal gun is limited to only surfaces covered in moonrock... So, its essentially useless outside of the lab.