i'M A NOVICE AND WOULD LIKE TO KNOW WHICH CAMERA WOULD BE THE BEST, THE GL2 OR SL1S. I'M FILMING AT DISTANCES OF 500 YRDS SOME TIMES MORE SOME TIMES LESS. WHICH CAMERA WILL GIVE ME THE MOST DETAIL AT SUCH DISTANCES?

For wildlife I would use an XL1s with a huge Canon photography lens which will cost you more than the XL1s itself.

It's almost impossible to get usable shots from 500 yards. Shooting through that much atmosphere causes serious degradation of the image.

See http://www.dvinfo.net/canon/images/images09.php.