That's a matter of taste. But the great thing is, this is my post, so it's my taste!
Its going to be very difficult to say MAC or PC is better because there are an infinite number of makes and models.
The release of Vista hast started a new era for PC's. The new operating system looks good. I won't please everyone, but its a great jump forward as far as I'm concerned.
I wouldn't say its better than MAC OS X, just different and I wouldn't call MAC OS X superior to Vista on looks either (in fact I feel it is starting to look a bit dated). That said the 'shiny' look of Vista can get a bit too much (especially with everyone adopting it)
All in all I'd say that for the OS, it's a 50/50 for MAC and PC.
Now lets get down to the hardware. Apple make slick looking machines, heck they make slick looking cardboard boxes that the machines come in. So what's going on in the PC world?
Other than a shift away from beige a number of years ago to grey/silver/black not much. The bulk of PCs come in various modern flavours along the same lines. They are cleaner, sleeker and smarter looking but still lack something that MACs have.
How do they manage it? Apple doesn't employ all the designers in the world so how is it that they are the only ones who constantly come up with a top class look.
One can't deny there is a great amount of innovation in PC's. Alienware PC's have a distinct look and there are thousand of modified cases made by enthusiast with one thing in common. They all look like shit.
There are some bright lights on the horizon in the PC world, and I would go as far as to say just as many funky looking PC as MACs (considering the amount of manufacturers there should be).
Noteworthy is the new Sony Vaio VGC-LS1 (though the name doesn't quite have the same ring to it that iMAC does). It's a desktop computer with a real Vista look (on the outside). It houses the computer in the monitor (much like an i- uh... never mind). The attached keyboard flips up to cover half the screen and when this happens a screen saver type thing displays date, time, weather and music now playing. One has to wonder it doesn't just have a normal screen saver (and use the whole screen to add other items of interest: new items, rss feeds etc.).
But in any case it's looks great (I'd go as far as to say it's a contender).
But where are the rest? Couldn't a couple more PC makers sit down and say “rather than adding a coupe dozen more processor cores and ramping it up to 10 zillion squizahertz, let make this one look good.
All in all, the OS is too close to call and what the PC world lacks in style it makes up for in shear numbers to suit everyone's taste. Compare that with Apples consistent and industry leading computer case design and I'm giving this one (boring though it is) a tie.