Hey dude,
I own a VX2100 and I've used the DVC 30..
So here's my advice.
If you plan on shooting in low light, go with the VX. Sure, 30 has night shot, but wouldn't you rather have a clearer picture without the night shot and are you really going to use night shot all that often?
If you plan on doing some extreme camera angles, go with the 30. Not only is it cheaper, but it's also much lighter.. The VX would be a shame to waste if you wrecked it.
If you want higher quality picture in day light.. of course, the VX wins.. but the quality between the 2 after your done editing, won't be all that noticable to the average viewer.
If you want to green screen.. use the VX.
If you want to buy more accessories.. buy the 30.
All in all.. the VX is better, but if your editing skills are good, you won't need to worry much about video quality differences.
Where to buy your camera:
I baught my VX new from Sony for $2,999 (us), but you can get a referbished one for $2350 from Sony with a 2 year warrantee!
DO NOT BUY FROM EBAY!!! I got scammed on Ebay for $1580 the first time I tried to buy a VX, so don't make my mistake! It sucks!
Shop around first.. don't just limit yourself to the 30 and the VX.. look into Canon as well.. the Canon GL2 series is nice too
