Obviously HD has a much higher resolution than SD.
However you will need a HD TV, and as there are no HD-DVD or blue ray recorders out yet.
You will have to use the cam itself for playback, and a min. P4 3,6 GHz or equivalent PC for editing. The later also is true for the cams which record to a HD or a DVD as they record in mpeg2 just as a HDV cam does which is not ideal for editing.
The HC3 performs exceptionally well at low light, but lacks manual controls. Many would not consider it because ot does not have any mic-in nor headphone-out, but there are some Sony Mics which can be connected though. The HC1 does have Mic-in and headphone-out but does not match inlow light performance. Both can also record in SD or you can downconvert the HDV to SD for editing.
DV or SD ( standard definition ) is much easier to edit,
even cheaper models may offer manual adjustments, a mic-in, a headphone out.
Could be still the better choice of not owning or wanting to invest in a top PC, HD TV etc.
please forbear if any of my infos are incorrect, I am no specialist, and my knowledge is limited to cams below 1500 USD. In that range Panasonic 3CCDs are tops, and the Sony HC1 and HC3 are the first HDV in that pricerange.
for more relyable info please check:
http://www.camcorderinfo.com/bbs/f5http://www.dvinfo.net/conf/index.phphttp://pana3ccduser.com/index.php