I only use the Stihl Motomix (pre-mix, non-ethanol, high octane fuel). Once I switched to it, I ceased having hot or cold starting problems--ever. In fact my saws get a bit of a clean and air filter cleanings and that's it now. I don't even know where my tiny tools to adjust the carbs are.
The MS500i is the hardest to start, but that mostly has to do with the need to pump/prime the fuel from the tank up to the engine the first time every day. It takes a lot more pumping that I expect, but once it has run for the day, it starts in a third of a pull.
The Motomix is way more expensive, but the fact that I don't have issues with my saws anymore says a great deal. Even the shaved head MS660 starts pretty easy on the Motomix, and I've never felt that it was detonating, even with the high compression.
Dan