Don't know about the standard battery on the Nexus, but with the Samsung extended battery the Nexus definitely outlasts the Charge. I think you can pick up the extended battery for like $25 last I saw and it doesn't really increase bulk to any noticeable degree, especially with a case (I'm using the Diztronic case I picked up off Amazon for $9).
I think you will be very pleased with the Nexus coming from the Charge. There IS a trade off in the screen; the colors on the Charge seem to "pop" more than the Nexus but because of the higher resolution, text on the Nexus is incredibly clear. I can read web pages in overview mode whereas I couldn't with the Charge without zooming. Another trade off is the camera. I think the Charge took better pics but the much faster shutter speed lets me capture more spur of the moment pics with the Nexus.