TypeKit has a lot of countermeasures to ensure that the fonts are used according to the license, and not by anyone who isn't allowed to or through proxy's or something. I don't know the details but had a run-in with this in the past, resolved soon by customer support. I'm guessing Adobe didn't care for creating a second serving system to serve up these fonts, or the licenses are still restrictive that it requires some added logic.
I don't know the current state of things, but a failed font download used to result in blank/transparent text in some browsers, ignoring the fallback font.
I abandoned Google fonts because of the annoying latency / flash on refresh. The Adobe fonts are smooth on my dev machine. That might be worth the difference under the hood.