75-300mm f/4-5.6 sharper than 70-200mm f/4???

[hotpoint]

I have a digital rebel (300d) and have a quick question regarding focus/sharpness. In July, I purchased the 70-200mm f/4L hoping to have a lens with significantly higher sharpness than the 75-300mm. I've taken about 2000 frames with it and it doesn't seem to be much, if any, sharper than my 75-300. I've done back/front focus tests, and it doesn't seem like the lens is doing either one of those things at close distances. Most of my photography is at a local zoo, so most focusing is done at infinity or at the minimum, 3ish meters. I don’t know if it is my imagination or not, but it seems like it isn't focusing quite right at those distances. Any input would be greatly appreciated!

jpeg, no post processing
75-300mm @300mm
1/2000
f/6.3
iso 400
http://www.fileden.com/files/2006/10/19/301893/IMG_1270-%281%29.jpg


100% crop of same image
http://www.fileden.com/files/2006/10/19/301893/IMG_1270_100%25_crop.jpg


jpeg, no post processing
70-200mm @200mm
1/1600
f/6.3
iso 400
http://www.fileden.com/files/2006/8/3/153231/IMG_5732-%281%29.jpg


100% crop
http://www.fileden.com/files/2006/8/3/153231/IMG_5732%20100%25%20crop.jpg