Hi,
That's a really good question, but here's an answer you may not want to hear...
It really DOES NOT matter which one you use...
What matters is:
1. You're passionate about what you're doing and
2. You're providing value to your visitors
The more years I spend in business, the more I realize it's NOT about *me* making money... it's about creating and providing something that my customers *value* more than the money they spend with me...
However, I tend to lean toward mini-sites because it's business a model that's inexpensive to create, can be run on 'auto-pilot' and still provides tremendous value...
Portals on the other hand have to compete with MSN, Netscape, About, etc... a tough business and expensive to promote properly.
A third alternative, which you didn't mention, is the 'community' site... where people who have a common interest chat and share resources...(kinda like SowPub:-) ...that can be a good choice but very time consuming for the webmistress (or webmaster).
That's my 2 cents...
-Dave
My Son said, "Dad it's not fair!" When I Make BIG Chunks of Money