I have used all three of the available computer operating system's - Windows, OSX and Linux. I have used every version of Windows since Windows 3.1, and while it has progressed along, my current version of Windows 7 Home running on my Acer laptop quad-core, 8 gigs of memory, 650 gigabyte hard drive seems sluggish at times. I run the defrag and cleanup unused files but it still seems to be sluggish.
Using Linux since starting with RedHat 5.2 back in 1998, it has matured well in my opinion. Also have openSUSE 12.1 on same Acer laptop as Windows 7 Home, and Linux seems to run quicker. Using many of same program as Windows - firefox browser just seems to be so much quicker - maybe though if I had more programs downloaded and installed like on Windows I might notice some difference, but I am guessing that even then it would still run quicker.
I also have an older - 2006 MacBook Pro - first generation with Intel Core 2 Duo using 3 gig of ram, upgraded original hard drive to 500 gigabytes, and though it is old and running version 10.6.8, it still speeds along. I know that OSX and Linux are more closely related than Windows, but it would seem to me that there shouldn't be a huge difference running two os's on the same platform. The MBP trumps both in that the hardware and os are designed from the same company, but I have thrown various versions of Linux on so many older computers over the years, and they would run pretty decent, long after Microsoft gave up on supporting that hardware.
Favorite os? I use Windows 7 Home a lot, though can get same work accomplished using similar programs for Linux and OSX. Don't really see an advantage for everyday usage, I used the MBP until the battery conked out and it wouldn't power up for a few days, then it started working again, so don't know how long it will last - while the Acer laptop gets majority of the work.
Smartphones are different beasts - Android uses a version of Linux, and IOS uses a version of OSX, which itself is related to Linux. Windows smartphone os not sure of that, and Blackberry is out with an updated version of its phone os.