In Hardware

I was wondering if anyone could tell me why my nes has poor picture quality? I noticed this the other day when my buddy and I were playing Contra on his nes. His was nice and crisp and it had better color. I then put it into my nes and the colors where dull and fuzzy. I just recently replaced the pins and I know my friend has had his replaced. I have also cleaned everything multiple times. The only difference that I can say between the 2 systems is that I use RCA to Hook it up and he uses the RF switch. Could that make that much difference? I thought that RCA would be better quality. I will take a picture the next time I am over at his house which should be today. I will post the two pictures to show the difference. Also I was wondering what the slot on the bottom is for?(the thing that is covered up by the removeable plastic cover)

Thanks

As far as I know, the port on the bottom of the NES is for a multiplayer link system that never happened. There was also a disk system that came out for the famicom that used it, but it wasn't released here either.

As for your picture quality, what are both of your tvs like?

I've always sworn by using the RF switch and I can't even remember why any more... maybe it's just out of habit :P