how can 1/10 " .....
 

how can a 1/10 of an inch difference in size of chipmake a difference.....

like why is a 1/3" chip better than 1/4" chip?

You have your math wrong.

1/3" = .33
1/4" = .25

.33 - .25 = .08

Also, it isn't just CCD size that makes the difference but pixel size as well.

The CCD sizes are all weird. The actual sizes of the CCD is a lot lower than the numbers. There was a thread on this a while back, which points to a nice article on dpreview.com about CCD sizes. But 1/3" is still bigger than 1/4" and so on and so forth.

Bigger chips are generally better. IF both chips have the same number of pixels, then the bigger chip will have bigger pixels. Bigger pixels means that there's less electrical noise and that more light will be picked up. This increases sensitivity/low light. The ultimate effect is better picture quality and better low light. There are a whole bunch of other factors that affect picture quality and low light, so you are better off considering those end results rather than looking at specs.

Some CCDs are designed to have extra pixels to give better stills. This tends to worsen low light performance. In a 3CCD cam more than ~380k is not that great (some of the panasonic consumer cams do that). For 1CCD cams, a 680k pixel CCD can give better low light than a larger 1080k pixel CCD (TRV22 vs TRV33).

what would be the difference in image quality b/t an XL1s and GL2 not talking low light, b/c i will light scenes

I have miniDV wedding footage. 1 wedding was shot with the XL1, the other with a GL2. Both sets of tapes have some well-lit scenes and lower light scenes using an onboard light. The XL1 footage looks fuller and richer, with superior color saturation---the footage looks like you are right there at the wedding. The GL2 footage looks weak and light, un-natural-like, when compared with the XL1 wedding footage. There was also smearing in the GL2 footage. However, the well-lit GL2 footage looked okay, but not as good as the XL1's well-lit footage. That's what I observed. I love the XL1 footage; the GL2 footage was not much better than footage from my 1-chip DVL9500. The difference reminded me of comparing 35mm prints with prints made from a medium or large format camera. But then a good larger format still camera costs more than a 35mm format camera, as the XL1 costs more than the GL2.

Notes: a Leica may cost more than a medium/large format camera; the GL2 operator looked more defective than the XL1 operator. :-))

whata bout vx2100 vs xl1s vs gl2

I don't have VX2100 footage, just VX2000 footage and some Sony 1-chip cam footage from a TRV30 and a PC5. So perhaps someone else can comment for you.