First off I am not a professional. I am a novice. I use video in education. I can only tell you about the ease of use.
I should have had more respect to the moderator. There is a better editor at AVID - "Media Composer" and I guess AVID xpress is a ripped out version of that. But I think that Media express is probably packed with things for making feature films. Even Avid Xpress seems to be geared that way and it does not seem at all ripped out. It seems to have a few more features and tools than Vegas.
I have both, but I always use Vegas since it is easier to use and seems to have no bugs at all, whereas AVID did things to annoy me (kept telling me my keyboard settings were incorrect, crashed more than once while attempting and failing to import, and post crash reboot without dongle caused annoying error messages). The need to use a dongle is a pain, since I sometimes forget to bring it home.
AVID supports more High Definition and otherwise high level video formats. If you have a Panasonic HVX200 then the latest Avid supports some of the P2 mxf files out of the box, whereas one needs to purchase the DVFilm Raylight plugin (195 USD) for Vegas.
On the other hand Avid does not support the low end video formats like mp4 or avi from my Hitachi woo handicam which is a pain.
It says it can do super things like image stabilisation and automatic white balance correction and even a rotoscope plugin (Boris Graffiti) but I never got it to import enough video to try them out.
That said I think that AVID may still be used by more broadcast media professionals. It has been around longer. It seems to have a lot of tools for workflow like somehow mergeing the video with the script. It is used by my local cable TV company and was recommended by a local pro production studio.
Hmm...Avid seems to come from the age of specialists. It brags about being used to produce "Lord of the Rings. It may well have more power but it strikes me as being a bit of a dinosaur.
Vegas gives the impression of being much more polished and slick. It seems to do everything, well, and is better presented.
So unless you need something that only Avid does, my recommendation is Vegas. It is also a lot cheaper.
That said, I am faced with paying 50 to upgrade Avid to get Panasonic HD import, or to pay $150 to buy the academic Raylight plugin and I am torn! I guess I will buy both.
By the way, if you are NOT a pro (other readers) the home movie editions (home movie and home movie platinum) of Vegas have the "show me how" which is super. It is the software only tutorial function I have ever been impressed with.
There is a discussion about this issue also at
http://www.videomaker.com/forums/viewtopic.php?t=3374