i voted mac for several reasons
first some background. i have had a 1ghz 1gig ram powerbook running osx since ~2002
1) i like the OS better - i find it more stable, user friendly, and it does what i want, and it lasts. i always have some problem with my windows os, IMHO the windows OS has a 1/2 life similar to uranium
2) build quality (not talking electronic components, but the plastic pieces that comprise the computer)- every dell, hp, home built, etc pc i have had has needed its doors, screens, hinges. my powerbook never had a problem (it has been dropped, thrown, stepped on, spilt on etc....)
3) Build quality - my friend spilt 12 ounces of Natural Light all over my keyboard (which is right above the logic board (aka motherboard)) well....the thing still works...i have not heard so pleasant a story from my other friends that were in similar situations.
4) price - over time my mac is cheaper and still runs reliably (you can do the math below to see what i spent less money on)
$1300 powerbook (i think thats what i paid for it) used since 2002 - no problems no need to upgrade.
$500 dell lasted 2 years before parts fried
$700 hp lasted 3 years (screen broke)
$300 home built is on 3 years....
4)It Just Works.