AVCHD vs HDV

My A camera will be the Sony EX1, but I need a smaller B camera for certain types of unique perspective shots (crammed areas, mounted on kayak, underwater shots, attached to fly pole, etc.). I was looking at the Sony HC7 and Canon HV20, but I need the Sony for the infrared Super NightShot feature (for around the campfire and inside my tent, etc.). I noticed that Sony just announced the Sony HC9 and has the option of recording to MiniDV tape or to a Memory Stick thing. Ideally I'd like to stay away from MiniDV simply because the EX1 is tapeless and I don't want to buy an HDV deck just for some B camera footage from a lessor camera (the decks cost more than the camera!). But it appears the Memory Stick records in an AVCHD format. It still says it records in 1920x1080, so I'm not really sure what the deal with AVCHD is all about. Then I saw a new Sony HDR-SR12 model that is a hybrid 120GB harddrive and Memory Stick model, which can record to either media. I'm thinking if this is a good format, as good as MiniDV, it would be ideal.

Any thoughts about these camcorders and HVCHD in general? Gracias.