It depends on your needs. vba is a portal system. vbcms is an article system.none of them can be compared to a real cms like for example joomla. If you need a portal system, then use vba.

A portal page is a a home page, which shows the users featured / important content from the rest of the site or links to that content. Mostly using blocks / modules.

What you need is a real CMS like Joomla or Wordpress and can not be done with vbCMS nor vbadvanced out of the box. It is possible to hack vba / vbcms enough to show whatever html content you want.

Joomla is always free.

No, there is no Joomla-VB bridge... it would be a major pain to keep a consistent theme across the two.

Static pages are pretty easy in the vBulletin CMS, if that is what you need it for you'll be fine with the suite. I haven't used vBAdvanced for VB4 so I don't know if it's easy(er) then vB CMS or not.

I would say it would be extremely difficult to make joomla look like vbulletin or vice-versa. The navbar, breadcrumbs, footer- this would all need serious custom programming and designing. If you intend to use joomla forget about having the same style across both platforms. You can maybe have the same colors but it will never look like the same product.