I believe the general consensus (which you'll probably find in various posts around here) is that the 4805 has a little better contrast and the HT410 has a little more brightness. The HT410 may also show more RBE (rainbow effect) due to having a 2x color wheel instead of 4x. In the HT410's favor (if memory serves) is a less expensive replacement bulb. OTOH you can probably get a 4805 and a replacement bulb for the price of a HT410 + 76" screen + 30' cable at the moment, since the current $995 deal on the 4805 includes the screen and cable.
I have a 4805 (and love it) and I believe that's probably the single most popular projector around here, but there are a few HT410 owners around so you might be able to get some direct feedback. There may be a couple of other models you should look at as well.