Well since we're being honest
My gaming PC history went as follows
AMD Athlon XP 2500+
AMD Athlon 3500
AMD Athlon x2 4200
Intel I5 2500k
So I have been both sides of the fence, so here's my honest opinion. My AMD chips were a million times easier and nicer to install, I prefer their board layout with having the pins on the chips. Installing my Intel I almost had a mini-heart attack putting that in. Stock fan I found my AMD performed quieter and cooler than my Intel Stock (I eventually moved to my 3rd Party Coolermaster fan for this reason)
Performance wise I felt AMD were the right choice back in the day but there's no denying that at the moment Intel's Sandybridge/Ivy bridge CPU's are better bang for buck. To the average user though, there's a good chance they'll never see the real world difference but I spend a lot of time in CPU intensive applications for development.
What I do miss about AMD though is their consistent chip sockets >.< Sticking with Intel I fear I have to buy a new motherboard and ram if I ever wanted to upgrade just the CPU. So that's definitely a plus to AMD.
Graphics card wise my history goes:
ATI All In Wonder
Nvidia Geforce 440 (Classic card)
Nvidia Geforce 5200
ATI Radeon 9700 (Fantastic card)
Nvidia Geforce 6600gt
Nvidia Geforce 7800gtx
Nvidia Geforce 8800gts
Nvidia Geforce 8800gt
Nvidia Geforce 560ti
Nvidia Geforce 680
So I'm a little bias here, graphics card I find comes down to the time of release and drivers. I like both sides here, I'll go for whichever 1 is best bang for buck at the time. What normally happens though is AMD will release and a few months later Nvidia will release something slightly more powerful at a similar price or vice versa. It's just always worked out that I got Nvidia. What does bug me though is the AMD cards are generally much bigger and hotter than the Nvidia cards. For example my friend's 6950 is MASSIVE compared to my GTX680.