No idea. Care to do a benchmark? I guess it will run slower if compression is turned on, but without compression - I'm not sure, there probably is not much difference.
I never noted any difference. The easiest way is to use a resource file so I'd stick to that unless you want to update your qml without rebuilding your project.
Depending on your target platform (cpu & IO) and code one way or the other will be faster.
Benchmarking is the only answer to the question, and that answer will be only valid for your system. Also, it depends on how you define "runs faster" and on your actual QML, I'd wager.
