I dunno about BEST, but Ulead's DVD Workshop is a decent app, and the one I use for my fairly simple needs. It doesn't really integrate with Vegas, but I don't use it that way. I just take rendered MPEGs, and author the DVD in DVDWS. One nice thing - it DOES automatically go to the next MPEG in the play list, though there's a second or so of pause.
Virtually all prosumer authoring programs have their own set of limitations/problems. It's a matter of finding the one that has the feature set, functionality & lack of bugs around your needs.
Personally I am using Pinnacle Impression Pro & ReelDVD until DVD-A comes with better navigation control etc.
Both are good apps. If you want the BEST alternative (at this time) from DVDA, I'd recommend DVD Studio from Apple. Doesn't run on a PC, but it's a brilliant software app. Best authoring tool I've used, and I'm an alpha tester for Workshop 2. Workshop 2 is a great app too, and very feature-rich. For sub 5K, it's the best PC tool out there. But DVD Studio is still better, but not by much.
DVD Lab doesn't use an encoder. It requires you to bring in either mpg files which it demuxes or separate mpv and mpa files. It offers you a tremendous amount of flexibility, but it leaves all the encoding to you.
Then workshop or DVD Lab is the best alternative for you. Encode to MPEG in Vegas for DVDLab, or import avi into Workshop. I don't recommend encoding in Vegas and then dumping to Workshop, unless you render the AC3 file also in Vegas. Even then, occasionally Workshop will run the file out of sync.
I have downloaded DVD-Lab and spent several hours evaulating the program. The interface and flexability is fabulous. However, I am having a lot of program crashes. For know reason at all the program closes. I would be looking at the screen and poof the program shuts down. No warnings or OS errors, nothing.
Have you had good luck with this program? I really would like to get this program to work for me, but after looking at the postings on the DVD-Lab fourm I'm getting a little nervous. Kind of like when I was using Studio 7 before switching to VV.
I have never had DVDLab crash on me, but it does seem to be an issue with some folks. I don't have an answer for you as to why it's crashing.
Obviously, DVDLab isn't for everybody, it is a "work in progress." I believed in it enough to have bought it to give Oscar some operating capital to develop it further. I have (and use) other DVD Authoring software, like Sonic ReelDVD, Adobe Encore DVD and a couple of others, so I'm not putting all my eggs in one basket. I like DVDLab and it was worth $100 to me to see how far Oscar can take it. It already works really well for me.