I'm looking to use Joesfin Sans. It's listed on Google web fonts. I also have the .eot, .svg, .ttf and the .woff. This means full compatibility with the files (as far as I know).
My main question is: which is better? Does Google Fonts load faster? Is it more compatible? Or should I stick with the files?
If you want the quick and easy solution, embed the font loader code and move on. Google is frequently adding more options/features to their service.
Personally, I prefer to download the files from Google and work with them manually. Since there is a Google UI specifically for downloading your selected fonts (and from reading the license agreement) I believe this is legitimate use, but I'm not a lawyer.
Why do I do this?
I have experienced latency when accessing Google fonts (200-300ms). While this isn't terrible, most of my server environments respond faster and a font is an important prerequisite for a page. Any benefit from hitting a separate domain (i.e. parallelization to different hosts by the browser) is lost.
I've manually trimmed the font files to remove all unwanted glyphs. This results in a smaller file size.
IE8 support--it appears the .eot doesn't always get downloaded.
These reasons are mostly anecdotal but I have been much happier managing the font files myself.