The DC4800 is more of a semi-pro type camera, with all the nifty features you could ever want. The DC290 is something of the next step up from the DC280/DC3400, with numerous additional features and extras.
The DC4800 is the most expensive of the three, weighing in about $100 more than the DC290, which is in turn about $100-$150 more than the DC3400.
Decisions, decisions, decisions...