Apple seem to be less interested in comparing themselves to MS and PCs in general these days.
In ~2005 their entire marketing was based around trying to sell you a Mac as a PC replacement "Your next PC should be a Mac".
I guess they are less interested now because it's a smaller % of their revenue and most of the people who would want/can afford a Mac are already giving them plenty of money so there's no desperate need to increase their market share in that area.
Microsoft has zero market share in the table market ("there is no tablet market, there is an iPad market"), and a very small share in the mobile phone market.
When you are #1 in a market, you don't do comparisons.
The Apple Stores are probably the best marketing the Mac can ever get. So it's better for Apple to spend money on the stores than on making TV ads for the Mac. And so they have: http://www.asymco.com/2012/06/25/the-face-and-the-brand/
It's pretty clear that the next Microsoft v. Apple war is being waged in the tablet market (the show is over for cellphones -- Apple won). Traditionally Microsoft hasn't done well at competing with Apple on their own turf (mobile, mp3 players, etc), but it'll be interesting to see what the Microsoft Surface means for all of this.
Apple won big in smartphones, but Android has a bigger marketshare. Competition between all smartphone vendors have made the customer the biggest winner in any case.
Of course it is relevant. A large Android market share keeps Apple on it's toes and as mrich said, consumers win. It also means that although Apple is winning by profit margins at the moment, they may not be in the future.
If Microsoft's Surface and/or Windows 8 RT take off, then we may see an increase in Windows Phone 8 marketshare. Why? Because of syncing, similar interface, possible app sharing, etc.
maybe. I've currently got an iPad and an Android phone, and i don't have any problems switching between two different mobile OSes. I initially bought an android tablet because i thought that syncing and app sharing consistent interfaces would be a big deal, but i sold it and bought an iPad because it's a better product. Having an iPad hasn't made me want an iPhone.
Also security on the whole has improved across all platforms.
When Apple began to market themselves as immune from 'PC viruses', the Windows platform was besieged in drive by downloads and massive, highly publicised infections.
In ~2005 their entire marketing was based around trying to sell you a Mac as a PC replacement "Your next PC should be a Mac".
I guess they are less interested now because it's a smaller % of their revenue and most of the people who would want/can afford a Mac are already giving them plenty of money so there's no desperate need to increase their market share in that area.