Which SNES to keep?

I recently bought a phat, SNES with no yellowing to replace my original yellowed SNES.  I believe the one I just bought has the small motherboard since it feels a lot lighter than my original one.  The problem is when I hook it up with a composite cable, I get a weird line down the middle of the screen, similar to the picture below.  I tried it with S-Video though and the line is not there.  



My original SNES doesn't have any graphical problems but it does have the yellowed case.  I thought about switching shells, but will the large motherboard fit in the newer shell or will I have to do some mods to make it fit?  

Are there any benefits to the big or small motherboard other than weight?

Are you opposed to taking your yellowed SNES apart and use something like retrobright?

http://retr0bright.wikispaces.com/

^^ I thought about that, but I read that the yellow doesn't completely come out.  I guess I can try it out.

For your green stripe problem, might I recommend getting the capacitor kit from Console5.com ? You'll have to open it up to see which version of the mother board you have. Here's a tutorial video:

https://www.youtube.com/watch?v=_m73rfrLd5s

^^ Thanks, but that seems like more work than I want to put into it, lol.

I would just peroxide it instead of retrobrite, easier and cheaper.

http://www.geekwithenvy.com/2013/07/how-to-make-a-yellow-snes-look-new/

I'd clean the one you want, they all will yellow to some degree eventually anyway, might as well clean one up now.

Good luck man, I wish I still had my Snes, there was some good games back then.