I would say there are a couple of other serious advantages in favor of PPro:
-Rendering performance: Vegas is just slow to render – even V.6 which is improved. PPro on my dual Opteron is very quick to render.
-Integration: The Adobe suite offers some serious capabilities when you use them together. I find the flow is powerful.
-Stronger 3rd party support: There are just more H/W and S/W options for PPro. Vegas is doing a lot better but still not as widespread as Adobe.
There are more but these are the broader issues.
gl