Thanks Steve. I've played with both and I'm inclined to agree with you. I give the edge to premultiplied.

Depending on what you're trying to comp I'd suggest doing the whole thing in AE. The upside is cleaner results, less work for Vegas and you can use a smaller file sized codec out of AE. The downside of course is you're stuck with the result without going back to AE.
Simple stuff like text will be fine, fog, smoke and fire can be a problem comping in Vegas no matter what, the last one being a challenge in any app.

Bob.

I would like to do it all in AE but I lose some flexibility in time line adjustment that way. If I do the alpha channel only in AE then bring it into Vegas then I can slide my alpha along the time line a few frames here and there without affecting the entire main time line.

Little side note:
People complain about Vegas stability.... I keep crashing AE with my MTS files on render. Something about about the "converter processor" stopping in the middle of the render. AE doesn't seem to like my MTS files too much because when I convert to uncompressed and import to AE there are no issues. Vegas of course doesn't have that problem :)

"People complain about Vegas stability"

Its amazing about some of the complaints over the smallest of issues in Vegas,
when some of the other well known NLE's and compositors etc. out there crashes consistently and is unstable as HELL....I've used them all at some point and Vegas is the most stable one i have in the barn...Think about it, there is no NLE out there that can handle both Editing tasks, High end compositing and Audio editing under one
roof and do so without the slightest of hitch.

For Motion Graphics, I use Quicktime (PNG+Alpha) from AE -> Vegas. If you need more flexibility, you could actually export AE layers individually for further compositing in Vegas. For video, I use Neo Scene for AE -> Vegas.

"Its amazing about some of the complaints over the smallest of issues in Vegas,

LOL.
I can't even begin to tell you how many times I've crashed AE in the last 48 hours! Quite startling too... I never really used anything except Vegas for the longest time so this crashing stuff is all pretty new to me.

"I use Quicktime (PNG+Alpha) from AE -> Vegas. If you need more flexibility, you could actually export AE layers individually for further compositing in Vegas. For video, I use Neo Scene for AE -> Vegas."

maybe this is a lot like shooting myself in the foot..... but I try to avoid anything with the term "quicktime" involved..... I HATE it.

The first thing that bloody quicktime player does is take over your computer and change ALL of your program associations..... without even asking you. The last time I installed that stupid player... I spent the next 2 hours re-doing all the associations in both windows AND firefox. Apple can take its quicktime and..... well.... you know.....

"Apple can take its quicktime and..... well.... you know....."

LOL....I understand your point, but once you install it and
sets its file association and preferences to suite your workflow in
the beginning, it then sits where it should.

blink, i use AE just about daily, never crashes... must be your system:)

I have had terrible trouble with AE4 crashing. Just a single 1 minute clip with a time stretch the only FX applied. Crash every time trying to render. Went back to AE3 to get it done. I still have crashes in AE3 but I can usually futz with something and get it to finish.