ProTools is by far the best program for audio Post. A Post user does not need advanced MIDI, so the extra features of Nuendo are unnecessary. Nuendo does some things better than ProTools, but because most stages and Post houses are PT orientated, it needs to be easier to transfer sessions from one system to the other. Digi has no interest in allowing their users to migrate from PT, so it is up to the other developers to facilitate things. So far Steinberg has been rather slow to realise this.
In any case, I don't know a single Post facility running anything but ProTools.
If so, PT is the big name, especially as they're owned by Avid who are pretty big in video editing.
But, there are alternatives out there...
AMS Audiofile- I believe there's a version that'll run on a PC, although they have their own hardware.
Pyramix (My preferred choice)
Just check out the features that are a MUST for you, and get assurance that your choice will do it- preferably from a user rather than a salesman! And if you're told "that feature will be available in the next version which will be out very soon", don't spend a dime until it's available!
Most the of the above have forums which are worth checking out to see what is annoying users.
I have Sonar and really love the program for creating music alone. But I am just starting to market myself for doing music for visual media and am concerned about possible compatibility/technical issues. You do see those things come up on the Sonar forum - guys under a deadline and struggling with Sonar's ability to handle some of those issues (although that's certainly not unique to Sonar).
I have done a few small projects and didn't have any issues but wasn't really working with a higher level person on the other end. They were more accommodating than I would expect from a bigger client.
I am not familiar with all of the suggestions above - so I'll look into those. As far as Pro Tools, that would be a matter of updating hardware too. If there is a viable workaround for that, I would like to look into that (as I really do love working in Sonar), but don't want my software to be a detriment to possibly getting work either.
Nuendo. Cheaper. More potential horsepower. More flexibility. Higher return on investment. Better automation. More control surface integration options (SmartAV, Euphonix, WK Audio, not to mention all of the Mackie knock-offs that can take advantage of the full MCU protocol plus Nuendo's extensive remote command set - with Pro Tools you're lucky to get HUI control for anything other than their overpriced controllers).
Turn off the features you don't use and you'll never know they're there - takes all of five seconds to tailor features and menus to your paricular needs. Now that they license the creative/music material separately in the Nuendo Expansion Kit - you don't have to pay for funcitionality you don't want/need.
Get SSL Pro-Convert v5 for native Pro Tools session interchange and a few Mac-friendly exchange apps like MacDrive and StuffIt Deluxe and you're done. I've been working that way for a while now and no complaints.