> Better performance

Counterbalanced by the fact that if you just throw any old random font file on your server, it'll quite possibly be larger (in some cases considerably so) than necessary. So now you need to subset/split up the font files yourself, which takes some extra work (and the various online subsetting tools I've found often don't allow proper control over which OpenType typographic features to keep, sometimes mangle ligatures, etc., so I had to hack something together myself based on the Python fontTools), especially if subsetting a single file isn't enough and you actually need to split the fonts into multiple files.