But it does not make much sense to compare these versions - Windows started being a modern OS with Win 2000 and arguably already Windows 95. These were the releases that won them the desktop dominance. That's probably why you are feeling Windows is "older".

And because you still see people using XP from time to time, but how many % of the tech population have ever seen OS X 10.0? I got into Macs seven years ago, and I only know the 10.3 installer because I'd intentionally bought an "oldtimer Mac" later on (iMac G4). Everything before that is a web of myths to me.

Enough of them do. When OS X 10.0 was released I went to a powerbook users group install party and installed that sucker on my graphite iBook DV. I still have my Public Beta disc.

IMO you still see people using XP because that was the peak. It was certainly better than Vista, I cannot give an unbiased review of Win 7.

I think XP might really have been the peak in usability, but under the hood, I can only guess that Windows 7 has gotten much more secure. After all, improving security is pretty much the only thing Microsoft has done between XP and Windows 7.

That's probably right, I know they have improved security greatly in the last few years.

Windows NT was much older, from the early 90's, which was the basis for Windows 2000, XP, Vista, and Win7. The subsequent releases were mere upgrade and fixes of the original OS.

Yes, but Windows NT never was popular outside out business.

So starting with OSX, Apple has introduced 9 versions and Microsoft has introduced 4. Now, granted, you can't actually have upgraded from 10.0 to 10.9 because of the dropped hardware support, but it would be interesting to compare the cost of upgrading through all the versions.

Win2K was marketed to businesses as the last version of NT before consumer-pro unification. WinXP picked up consumers from Win98 who skipped WinME.