what is the difference between HD and HDV?
HDV is a cheaper than DVCproHD and HDcam..HDV is cheaper more of a home movie approach to HD.
what is better 2.96mp or 6.1mp? do mega pixles help with video quality?
Camcorders don't use mega pixels, they use mega bytes per second.
if it is HD does that mean you can only film HD or can you change a setting and shoot in a normal mode?
do they both take pretty good pictures?
I have no idea with the cameras you asked about. Why would you want to?
do they have decent battery life in any weather condition?
Any cameras battery will weaken...especially over time in cold weather situations.
As hyped up as HD is right now do not waste your money on a consumer style hdv video camera. It's not worth it. If your really looking to get into filming look into the cameras I suggested in the other thread.