Which should I buy?

for short movies generally... i need smth with good nightvision

A1U has the normal "Sony SuperNightShot" green monochromatic odd infrared feature thing that is fun maybe once or twice, then useless - but it does work in zero light. Makes ppeoples (and animal's) pupils look really strange and grainy.

I don't think the Panny has that... but it should be OK (likely grainy) in low light - but zero light will be... um... really dark.

In either case, you can do either a camera mounted light or a non-camera mounted light... Both cameras have external mic-in jacks, so that's good...you will need at least one shotgun mic and one or more clip on-lavalieres...

If you are "making movies", you can control the light...

yeah but which one would you choose?
And can the Sony convert the HD to SD when needed to be edited on a lower performance system? And doest it use normal miniDV tape or the more expensive HD ones.

an HDR-HC1 - and I like it a lot - and I have computing horsepower to edit hidef... when the editing is done, and I burn a DVD, it downsamples to standard def. The next step is to output back to the camcorder onto tape because that is high-def (if it was recorded in hidef to begin with). Later, when I get an HD DVD or BluRay burner, I can re-import that finished project and export to HD DVD or BluRay - in the mean time, if I want to watch a project in hidef, I just connect my camcorder (using the component video and the stereo audio cables) to a HDTV... The camera has an option to record in hidef or standard def (16:9 or 4:3). Pretty much all the hi def camcorders can do this. It depends on the project on which format I choose.

Yes, I use "normal" miniDV tapes when recording in he definition and I do not use the "special" HD miniDV tapes.

The few things I don't like about my HDR-HC1 (similar issues - other than the XLR connections with the A1) I have learned to work around:
** The tape mechanism is a bottom loader, so when the camera is on a tripod, it can be a challenge.
** Use a "spacer" to lift the camera off the quick-release tripod mount.
** The HC1 is the consumer version so only a 1/8 inch mic-jack in - so I use a BeachTek DXA-6 XLR adapter (the A1 replaced the flash with an XLR adapter)
** I have a 2x tele adapter so I am not limited to the 10x zoom... and I have a 0.6x wide angle lens, so framing is OK in tight spaces.
** I am not real thrilled with the combo manual control ring - I can do either manual zoom or manual focus - but not both at the same time. I do like the camera - and for my learning, it was perfect - but I know now that either the Canon XH A1 or the Sony HVR V1 (or the HDR FX7 - consumer version) would be a great addition to my arsenal... and I would keep the HC1 to work with whatever new camera I (hopefully) get later this year. I guess the HVR Z1/HDR FX1 would make the short list, too, but their zoom is not as good as the V1/FX7...

Now that I have been in the hidef world, I don't know that I would go back to standard def. But if I did, it would be with something more like a Panasonic AG-DVX100 or Canon GL2, Canon XL2 or Sony DCR-VX2100... or one of the previously mentioned hidef cameras using theor standard def mode.