DVCAM v DV v External Recorder
 

I understand that DV should have better (i.e. uncompressed) sound than DV, but does DVCAM have better audio than DV (apart from dropouts)?

I need to record a choir, plus a band and a string section for our movie, & we don't have a separate audio recorder. I'm hoping DVCAM or DV will provide equivalent quality to a recorder (or perhaps better quality than one of those SD-card recorders, which I presume compress sound like HDV).

DVCam basically uses the same encoding as DV so there is no quality gain there. The inputs and the A/D converters should be better with a DVCam camera than on a standard DV camera and DVCam should be less prone to dropouts as the tape runs faster.
Although the specs are the same as DAT (16 bit, 48 hz) - the quality isn't quite as good but only if you are really picky. Stay away from HDV for any audio purpose.

Both DV and DVCAM record in PCM audio. The only difference is that DVCAM supports "locked audio" for the 16-bit 32kHz and 16-bit 48kHz modes.

All this means is that, for each frame, there is an exact number of audio samples that must be present. For unlocked audio, the number can vary from frame to frame - but the average number is still tightly defined.

You shouldn't notice any differences between the two when using the same piece of hardware. However, as you note, DVCAM offers better resistance to drop-outs etc.

Not necessarily so. The Zoom H4, for example, has several MP3 recording bit rates (some quite good), as well as uncompressed PCM recording at 16 and 24 bit, 44/48/96 KHz sampling rates.

If $300-400 is within reach, you should take a closer look at the Zoom, the M-Audio Microtrack, whatever the Edirol is (?), etc.

Although DV, DVCAM and HDV audio are all generally OK for dialog, you can do better for music with an external recorder. Which will also require decent mics, cabling, perhaps a mixer, and someone who knows what to do with the gear.

Its the Edirol R-09 ... it can record at 24bit 48KHz PCM (i.e. better-than-DV).

One advantage of the SD card recorders is that they have no moving parts so zero mechanical noise, whereas the cameras have various hums and whirrs so that you ideally need to move the mike away from them.