Windows XP release date: October 25, 2001
Mac hardware from 2009 is still very capable for what most people use it for: office suite, email and web browser.
(I could argue a optimized Windows XP computer from that era could still do well with today's software, but if someone is still using Windows XP on 10 year old hardware, it's probably running subpar)
I guess you would compare OSX version with service packs though, but I don't think that's fair.
Honestly Apple is playing the obsolescence card much more aggressively than microsoft, because they can. I installed Mavericks on my 2GB RAM macbook pro, and my laptop is already obsolete, it's very sluggish. I would GLADLY trade mavericks for windows XP. And I'm sure Windows 7 runs very well with that amount of ram.
It's free, but only after you pay for new hardware.
I finally had to buy a Mac mini just so I could do iOS development. But every Mac I buy now, I just have to plan on running Linux on it in a few years.
https://www.apple.com/osx/how-to-upgrade/
If you only had Leopard you had to spend $20 to get Snow Leopard first before getting the update to Mavericks.
Edit: I should say that not all Snow Leopard machines can be upgrade to Mavericks, a bunch of the 2006 models can't.
If upgrade/downgrade issues are your primary concerns when purchasing hardware then Apple is probably not the right hardware vendor for your needs.
How the fudge is this something that Apple gets away with when nobody else upgrades you to a pay-for, latest OS for free?
Yeah, it sucks when software becomes unsupported and you might have to update or change in the smallest degree and there are plenty of reason to hate Apple (stupid walled garden, OpenNI, etc) but this isn't one of those reason.
For me, it's just another example of the kinds of things Apple can get away with and no one bats an eye. 20% of all Mac users must upgrade or risk being unsecure. So what the upgrades are free? What if you have a critical piece of software that isn't compatible with the latest OS X? Or what if your hardware can't support an upgrade?
EDIT: Some people are making comparisons to MS dropping XP support, but I don't think that's a fair comparison since XP was released in 2001 and Snow Leopard in 2009.