the main difference in any of those in that price range is the pixels or detail on the screen. I myself have eagle 320 and a cuda s/gps...cuda will soon be replaced though when I get my Garmin 76cxs.
You'll get more detail with the 480 as it is 480x480 the x96 is 320x320 both on a 5" screen...the comparable lowrance to eagle would be the 480 and the x135....x135 is pretty pricey though...but the lowrances are better units than the eagles in my opinion.
Humminbird I do not know much about...although I know they make some good units, better than they used to.
If it were me I would go x96 and if money allowed I would go x135...but for 100 more you could jump from the 135 to the 510c and get color and 480x480 pixels...I think I'm going to wait and try to get a x510c myself. Goodluck and look at some screen images and see what you think you will want.
What are your goals?? Are you just locating structure and such?? Or really want to get detailed?? If your on a budget...as I am...I would go with the eagle 480....you'll get a clearer picture of what you looking at for a better price...although the lowrance is probably a bit more dependable.
"But if serving the Lord seems undesirable to you, then choose for yourselves this day whom you will serve, whether the gods your ancestors served beyond the Euphrates, or the gods of the Amorites, in whose land you are living. But as for me and my household, we will serve the Lord.” Joshua 25:15