I originally thought enabling multisite would be the way to go with this but further reading (namely this) has made me not so sure.
Do you really need a network?
The sites in a multisite network are separate, very like the separate blogs at WordPress.com. They are not interconnected like things in other kinds of networks (even though plugins can create various kinds of interconnections between the sites). If you plan on creating sites that are strongly interconnected, that share data, or share users, then a multisite network might not be the best solution.
For example, if all you want is for different collections of web pages to look very different, then you can probably achieve what you want in a single site by using a plugin to switch themes, templates, or stylesheets.
For another example, if all you want is for different groups of users to have access to different information, then you can probably achieve what you want in a single site by using a plugin to switch capabilities, menus, and link URLs.
This is what I'm thinking of doing:
My domain, Aless.ca is currently just a painfully boring blog. I thought I'd like having everything all in one place, turns out that's not so. So what I want to do is have everything as-is (using a theme like this http://okaythemes.com/themes/scribe/ or maybe sticking with Twentyeleven or another free theme) but also have a blog that utilizes all those pretty post formats I'm gaga for (using something like this Kendura from Themeforest). Please note that I am not actually considering paying for two themes, but I haven't taken much time to explore my theme options).
So the main theme, in this example Scribe, would have all my political posts, portfolio, etc, while Kundera would have life-posts like "Ooh I went to supper with John and Jane Doe and look at what I ordered!!!!" and other Tumblr-ish things.
My question is, do I need to multisite or no?