I'd still go with a bat. First, it'd allow me to keep YOU away from me (at a distance). Second, I'm pretty damn strong. IF I connect, you aren't deflecting it. It will break something or put it to sleep so you can't use it. Third, you're implying that I'm just wildly swinging. A real fighter won't do that. He'd pick his shots, and have just as many openings as the guy with the knife. As i said before, you're going to have to be quick and perfect to hit an organ to slow me down. Finally, you can do more with a bat than just swing it. You can deflect with it, you can block with it, you can jab with it, you can push with it.
A knife? To use it effectively you have to get close and you can only slash or stick. It's small, too. If you're lucky, or a master trained knife wielder, you MIGHT hit something vital and slow the person down - but that would be right before the guy hit you in the head and beat you to death with the bat.
Baseball bat, all day long.
Never argue with an idiot; they'll drag you down to their level and beat you with experience." ~ Anonymous