Here's a chart
http://www.xbox-scene.com/modchips3b.php
X-ecutor pro can flash 4 bios on the chip. X-ecutor lite can have 2 bios on the chip. Also x-ecutor lite is preflashhed, so you just have to install it.
Other than that, the chips basically do the same thing. But as of now, x-ecutor is cheaper.