This should be a discussion about operating systems, not hardware.
As I said earlier in this topic, I think Linux is the best out of all of them for the simple fact that it is the most flexible. Since it's open source anyone can use the kernel for whatever they want. In terms of it's use, it's probably more widely used than any of the other two, probably even combined.
And before you say that Windows is more widely used, considered how many embedded systems (ie. Devices like cellphones, etc) that may be utilizing the Linux kernel for it's OS.