Hi Nancy,
IMHO, governance and requirements should drive decision that 100% of the time. Let me give you some examples...
If you are referring to the managed documents section of your portal, i.e. sites where managed corporate ip is stored and consumed, I believe a consistent look & feel is imperative to the findability of that information. In most cases, I find it best to use the Publishing Site template for every site in these collections and the site provisioning process is highly governed.
If you are referring to the management of projects and initiatives, I also believe you will find the need to govern the provisioning of sites and content placeholders. Don't just allow anyone to create sites in this space for many reasons. Some of these include security, finability, and the need to produce consistent roll-up of information in the future.
If you are referring to the creative/ad hoc/collaborative space, then initially provide them with a small list of site types to choose from during the reqest process. Initially remove them from the need to understand the technology difference and use names such as Social Event Site, Collaboration Site and Meeting Site. The Intranet Implementation team will have previously chosen which SharePoint Site Templates will be actually used for each of these.
In short, try and remove the business user from having to make the site type decision based on technology. Allow them to tell you what the business need is and a site is consistently provisioned for them.