The MacOS (now supplanted by osX) has always stood apart. It comes from a single company and is designed to be run on that company's hardware. (Like Sun Microsystems, which alas is no more.) Buyers who get macs in general do so out of personal preference for both side of the experience -- they like Apple's hardware and they like Apple's OS. They prefer both.
MicroSoft Windows came to predominate the PC industry, achieving a de facto monopoly in the 1990s. But though the software came from a single company, the hardware came from any company that either licensed the OS, or built compatible hardware on which the OS could be installed (such as whitebox computer makers or home brewers).
MS-Windows was a buyer's only choice when looking at mainstream low-price PC hardware. Many schools and businesses standardized on the Wintel ecosystem in the late 1980s and through the 1990s. Thus many buyers who got Wintel PCs did so not out of a personal preference for MS-Windows but rather for a few other reasons:
This meant that there were significant numbers of buyers of Wintel PCs who were only (grudgingly) buying hardware bundled with MS-Windows because they had no choice, and not out of any personal preference for the OS. MS-Windows is just what came with the PC you got, it was the default option, and was rarely chosen for itself. Any gripes a buyer had with MS-Windows came to the fore, whereas the good parts of the OS were taken for granted.
This state of affairs led a goodly number of geeks to adopt Linux or one of the flavors of BSD (and later, when OpenSolaris was developed and could be freely installed on x86 platforms, Solaris).
On today's mobile platforms, we find a few OS choices:
Apple, as on the desktop, pioneered with the modern smartphone and touch-tablet. Apple makes its own iOS to run on its own hardware. Microsoft, quite late to the game, follows its previous model on the desktop, but also makes its own hardware; to date the company has had limited success in winning OEMs to license the Windows Phone OS, and even less success in licensing Windows RT.
Android here is like MS-Windows: Google's Android division writes the OS, and hardware companies license and adapt it for use on their own hardware. But since Google based Android on Linux, the OS is freely available, and an OEM can install almost any flavor of Android (excepting only the stopgap first tablet release of Android 3.0 Honeycomb) on their own hardware.
Android is like Linux. So many `open' geeks like it. But Android is also like MS-Windows in that it is controlled by one company. It also involves a new wrinkle to the game due to the devices being of necessity online: official Android OS releases include Google code that reports back to Google. Google knows who you are, where you are, and what you are doing with your device. And through Google's servers, so does the US Government.
There is another wrinkle here: there is fierce competition and rapid development in the mobile hardware world. So updates to the Android OS might not work on past hardware. More: most mobile hardware that hooks into a telco system is controlled by the telco (Apple is the exception here, and Microsoft is trying to cleave to that side) -- thus whatever version of Android that comes on a smartphone will only be updated at your carrier's desire, and will usually be larded with applications that serve your carrier's interests rather than your own as buyer. And each hardware partner in the Android world seeks to differentiate its offerings, and will add its own layers of user interface and application programs.
I like the look of iOS, and since I use a Mac, it makes sense for me to go iOS in any tablet or smartphone. But this only locks me in further to Apple's world. Just as I installed and played with various Linux distros on my PCs in the past, so I am leaning toward Android tablets. But then, they report to Googleplex...
Not sure, in sum, what I will do.