Optimus One: good build, Android 2.2 & 2.3 update coming soon, huge community support, standard resolution (more apps will run on it), looks good, good battery backup. but camera is not so good.
Galaxy Fit: 0.1" bigger screen, 5Mp cam (pic quality is lot better), Android 2.2. but the resolution is too low for such a big screen (pixelated), battery is small, no camera flash for good camera, little or no community support.