Consider that all TV will become digital in Feb 2009. If you don't have a converter box, or a HD digital TV, you will not recieve a signal. From my limited experiments, the digital TV will be much better than analogue, and probably a lesser antenna will do.
I have one of the mid priced Shakesphere antennas on the Tom Cat--and get 3 analogue stations. I used a flat plate antenna (RCA) which cost about $26 at Wal Mart on a new digital (Westinghouse 16"-$168 at Sam's club)--and got over 30 channels, without ghosts or snow. I got the same number of stations with the Shakesphere marine antenna. There is also a Phillips active antenna, which is about $39--and seems to work very well with digital--I have seen several boats using this--I have one, but have not tried it on the boat--it works well inside the house, but not much better than the flat (probably a frackel) antenna.
If you are in the city areas--I suspect that almost any antenna will work well with the digital TV's.