HV20/30 does not beat a DVX100B any day. I own both. The HV20 does shoot a nice picture because of the HD, but its a straight consumer cam with no manual control. When it comes to video, control is king. My recommendations based on your budget. (24p can be a pain to work with from this cam....you have to deal with a convoluted workflow)
Less than $1000...get the HV20. It is hands down the best cam you'll get for under 1k.
If you have around $2000, go for the DVX100B and learn to use its manual controls. You'll get a better picture because you'll have full control. I've seen some sick video shot on these. (It was actually the 1st digital camcorder to give 24p and has the most support edit-wise)
IF you have the loot to spend around $3500 than I recommend my personal favorite... the Panasonic HMC150. All the conrtol of the DVX100B, full HD (1080p and 720p), native 24p, shoots to inexpensive SDHC cards (I've managed to squiz around 3hrs of 1080p onto a single card).