i really hope that f/32 on the long end of the 75-300 is a typo... that's a really dark lens.
which camera do you have? i dont think the ef-s will fit on a full frame camera.
i dont know about the image quality on both, but the IS one looks like it has a better build quality. plus, the IS should be more than helpful when using the long end of the lens.
don't plan on using the 75-300 without a good amount of light.
u can get those lenses online for a lot less.
check
PriceGrabber.com - Comparison Shopping Beyond Compare