Vegas has lots of great audio editing features built in, and access to all of the same plugins in Sound Forge. An advantage to using Vegas is that it is non-destructive, meaning that the changes you make are not saved in the original file, and are completely reversible at the project level.
Sound Forge, on the other hand, is an audio-only editor that works in a different way. When you make changes or edits, they are applied to the original file, and once saved under the original name, cannot be undone. Don't let this scare you. Vegas allows you to open the audio in Sound Forge, perform your surgery and "Save As" a new take, which preserves both the original audio file and the edited file, that can be used selectively in Vegas.
That being said, I use Sound Forge for almost everything except simple volume envelopes, which I still do in Vegas. For one thing, the SF workspace is uncluttered and allows you to zoom in to the sample level, and gives you nice big "pictures" of the waveforms. Second, SF has some high-powered tools (Spectrum Analysis is one) that I use a lot. Although originally a two-track only, the latest Sound Forge 9 Professional will work with some multitrack files.
My typical workflow is to open the Vegas audio track in Sound Forge, work on it, and save as a new take. I generally have three or four takes saved by the time I am done, and can revert at any time.
If you don't need power tools, and are applying envelopes and effects and straight-ahead editing, go ahead and do them in Vegas. One huge advantage to working in Vegas is the effects automation feature, which allows you to do many things on-the-fly.
Well one thing I did not make clear is that I did want to do some audio and music work outside of Vegas, and then import and sync up as needed. I have Vegas Pro 8.1 on an 8 gig 64 bit machine, but it still sometimes runs slow, even with only 1 hour of video loaded. I am under the assumption that if I have Sound Forge (or other editor) that it would be faster and cleaner to edit outside of Vegas, then import and sync. Would you say that is a fair assessment? Are there specific tools or features that make importing Sound Forge files into Vegas easier than from other sound editors, or it does not really matter (I am seriously considering an Adobe sound editor as an alternative)?
Sound Forge is good, Wavelab is good, and Adobe Audition is good also - the latter not being as sophisticated as SF and WL but a lot of people love it. They all have their unique qualities and shortcomings but you'd probably be satisfied with any of them. And yes, an external editor can make things go a lot quicker and with a lot more precision as well. Download demos of all of them see which has the best fit for your workflow.
If so copy the audio tracks and paste them into another copy of Vegas for editing and when done close that project.
Drop the new .VEG project file onto the time line of your video project as a nested project. The nested project can be edited, if needed, by a right clicking the audio event in your video project.
Vegas being non-destructive allows you to try various plugs and settings to get the sound you want and tweak it later if needed. Forge, as has been mention before, is more of a surgeon's tool and you best keep a copy of the original file if you change your mind.
It really depends on the type of 'audio and music work' you are talking about.
Sound Forge is a great file editor for mono, stereo or multichannel files but it is not a multitrack DAW for laying up multiple audio events and tracks for vision.
Vegas, as a multitrack audio editing application (DAW), certainly covers most bases in editing and mixing audio.
It doesn't offer MIDI functions for music so if that is a prerequisite then a program like ACID or Adobe Audition (not Sound Booth) would be logical alternatives. You can choose to complete all of the audio for video in either or complete components and import them into Vegas and complete the mix.
If you want to begin editing in one program and then transfer to another, but maintain the individual clips and tracks, have a look at EDL Convert Pro. It will allow, at a significant dollar cost, you to translate your projects between most of the more common audio DAW software.
If you want to find out more about Adobe Audio products check out http://www.audio2u.comAudio2U[/link] The 'Building the Pod' podcasts are a great resource on Audition. Bruce Williams, a close friend of mine, is the webmaster on this site which he started it out of his own interest in the software and has been picked up by Adobe and lynda.com to run training courses on Audition.