For filming a wedding, I was going to do main stuff with A1P in HDV mode. For B roll, I was going to use my older camcorder: it can only do SD.

For the latter cam, should I record in widescreen mode, or just film normal 4:3 and do the widescreen conversion stuff (and meld with HDV from A1) in VegasMS in post?

Thanks

I would film in widescreen to keep everything looking some what uniform. I don't know if it works with Vegas but have you tried looking into Red Giants Instant HD plugin? I have had good results with the plugin. It takes SD footage and throughout a lengthy render turns it into HD footage that can be used as a B Cam. Of Course its not as clear as the original HD footage, but it gets the job done. I typically apply a Black and White filter and mess with the Levels/Curves adjustments to get it to look as good as it can.

If your b-roll cam can't do native 16:9 and it just crops off the top and the bottom, there's not much difference in quality between the two methods. Some people would recommend that you film in 4:3 and crop in post, so you can adjust the frame in post. Personally, I'd rather just film in 16:9 and frame it the way I want to frame it instead of messing around in post. So, there's not much difference, it's up to you. Just out of curiosity, what is your other camcorder?

By the way, check out this link, it gave me some pretty useful ideas about interesting things you can do with 4:3 video in a 16:9 frame.
http://www.kenstone.net/fcp_homepage/faking_it.html

The secondary camcorder is Sony DC110. It is still working well, is small and light, so don't want to discard it. I am hiring the A1P as I don't want to spend big$ on a camcorder that may obsolete soon!

For the latter cam, should I record in widescreen mode, or just film normal 4:3 and do the widescreen conversion stuff (and meld with HDV from A1) in VegasMS in post?

My advice would be to run the older camera in 4:3 mode in case you end up needing 4:3 output of the finished project. If you shoot widescreen in the camera you won't be able to get that footage back to 4:3 with any kind of quality, but the HDV footage would crop to 4:3 fine if you have to do that.

I'm not familiar with your other camera but I think the real answer is to do a test in widescreen mode. A number of Sony's consumer cameras actually had high quality 16:9 modes. One clue would be whether the camera can take high resolution still photos (1 megapixel or greater). If it can do that, chances are it will use the extra pixels to create a full quality anamorphic 16:9 image.

Shoot a few seconds of video in each mode, capture and compare. That should answer your question better than we can, since we don't have your camera handy :-)