Actually in my mind search is a criterion because the WSS search is not as powerful as portal search and portal search can feed off benefits like shared services and search multiple portals. OOB WSS search will only index that WSS site, which can be an issue for some clients.
I try to never bring in words like “portal”, “WSS”, “team site”, “area”, etc. into conversations with clients when doing requirements gathering. You tell me what you want and answer some basic security and existing content questions, and I will decide what is best for you. As for where to put things, to me it goes back to the basic who is the audience (large vs. small) how frequently is the content updated (static vs. short-term), and how secure does your content need to be. Additional items are how powerful of a search do you need, and does your content structure run deep (WSS sites don’t handle deep content hierarchies very well IMHO).
Once those questions are answered you can determine portal or WSS, then you can look to see if you have an existing site that the content would be a good addition to, or if you need to create a new area or WSS site for the content. And a lot of that depends on the internal structure and the purpose of the site. That is getting into usability and content organization and only someone with knowledge of the internal structure can determine.
Unfortunately I don’t know how much of this can be canned into a flowchart, unless your environment is already setup with buckets for sites and areas so you could go through one line of questioning and the end answer would be, it needs to be an area in this XYZ portal. If this is a site by site decision, someone with knowledge and understanding of not only SharePoint but of the environment would have to be used at least at the final decision level.