Wikipedia is faster than Google, for the common class of Web searches where you already know the name of the thing you're looking for: "tell me about Ipomoea". When you look something up by googling it, Google gives you a list of results (often including the Wikipedia page), but then you have to click on a link to get to the actual page. When you type in the URL of a Wikipedia page, it takes you directly to the result - and most of the time it's a good one.
Google's I'm Feeling Lucky feature is just as fast, but less specific. It takes you to the most popular or important page on the search term, which is often not the most informative - it might be someone selling it, or a story about it, or something named after it. None of these are as much help as even a mediocre Wikipedia page.
Of course Wikipedia URLs are a bit long to type. Fortunately Mozilla (including Firefox) has a feature to make it easier: you can teach it commands that expand to URLs, so "w Proteobacteria" takes you to http://en.wikipedia.org/wiki/Proteobacteria, and "g carnot cycle" asks Google, which refers you to Wikipedia, of course. This feature is intended for searches, but it also works for many other purposes. Until I wrote this paragraph, I thought Firefox didn't have this feature; I've been exploiting URL autocompletion instead. That's awkward enough that I wonder if it's any faster than using Google; I may have just thought so because it's more interesting. Blogging can be educational.
Curiously, when you don't know the name of what you're looking for, Wikipedia's search is not much help. In my experience Google, even without the help of a
site:en.wikipedia.org restriction, is more likely to find the right Wikipedia page than Wikipedia's own search is. It's that bad.