This is a question that many have wondered.
I have used MiniDV for many years. One draw back to this format is the real time required for capture to the computer, the storage and care of tapes and the limited re-use. Hard Drive Camcorders have many benefits. No tapes to carry, instant transfer to the computer and faster finding of wanted footage. The new Flash Memory based models are similar to the Hard Drive models, plus ease of archiving, and nearly unlimited re-use. There may be some conversion time from HD to SD. The DvD format based camcorders are a little tricky to edit from.

The PowerShot G9 has higher megapixels (12 vs 8) so cropping the photos will still leave you with a larger image to print. The zoom is also higher (6x vs 4x), this is always a favorable feature. Plus the G9 has Image Stabilization. Between these two, the PowerShot G9 camera should take care of all your photo needs and more.

A Digital -SLR will give you the best enlargements. A compact's sensor is a little bigger than the size of the eraser on the end of a pencil compared to the sensor on a D-SLR that is bigger than a nickel (both are square of course). Also the more megapixels you have the better the enlargements. This will also allow you to crop out unwanted areas in the photo and still keep a high enough quality photo to enlarge.
If you have a 10 megapixel and crop out 20% of the image you still have a 8 megapixel image left for enlargement.

Well....yes..kinda...sorta. You can play the video from the camcorder out to the DvD recorder but it will step down to SD (Standard Definition) quality. If your Camcorder is recording in AVCHD..and..you copy the file to the computer and burn a DvD with the file on it, that DvD should play on a Blue Ray DvD player in HD.