Little Fish, Garmins Blue series (100, 160, 240) are dual frequency, the 160 and 240 are both 500 watt rms (very important) and both are high pixel count, the 160Blue is 160X160 pixels, and the 240Blue is 240X240 pixels, they are identical units other then the pixel counts therefore the 240 does have a sharper image, oh yeah, $110 price difference to, is it worth it? I definitely think so.
If you're interested in picking 1 up anytime soon I would recommend hitting the Sportsman's show, our store prices are $239 for the 160 and $349 for the 240, I think there discounted 10% at the show. Hope this helps a little.