I know one is a color and one is not! What I would like to know is which one is the better fish finder?

I've got a 640c and it's not a bad unit at all.  Has all the regular Lowrance style menus and whatnot.  Better resolution than the X135.  The X135 has a bit more power output.  Six on one hand, half dozen on the other.  If you like color, buy the color.  If you can use black and white, buy that one.

i thought the same thing but i just pulled the trigger on the eagle because it was on sale, so was the lowrance, but the eagle had better resolution so i got that.

I returned my Humminbird 570 and picked up the eagle.  It's not a bad machine at all, in fact it works pretty good.  My biggest complaint with it was the screen.  I had to darken the contrast ALL the way to see it.  Plus I do a lot of night fishing and the backlight really wasn't that great at night.  I couldn't keep it for those two reasons.  The eagle seems to do as good as a job, with a much better screen.

I have an Eagle 320c and I'll never go back to monochrome screen again.