Here's a useful answer instead of shitty memes and jokes:
Nvidia:
+better drivers (not a bit better, a lot better, nvidia only users' anger at 2-3 games having problems in the past 2 years attests to that, I WISH it was only two games for me)
+better open gl support
+supports downsampling (this way you can have real AA in games that don't have a proper AA solution built into the game, which nowadays is about 80 percent of games)
+supports SGSSAA, another good AA method alternative
+ has physx support (gimmicky particles and cloth tacked on in games)
+shadowplay: game recording using the gpu to encode the video, which means you can record with no real performance hit , this is only relevant if you are someone who makes videos of their games, uploads to youtube or streams on twitch
+ lightboost support (eliminate the terrible motion blur of lcd monitors if you have a 120 hz monitor)
+supports the new gsync thing for monitors, which eliminates screentearing (I will not dignify the lag/stutter part, noone should play with normal vsync on to begin with), which is a really promising meaningful change in how monitors work
+better support for multiple gpus
+consume a bit less power/ performance
-costs on average 30 percent more because fuck consumers they will pay anything if there's no real competition
-rather weak compute performance (gpgpu stuff like gpu physics and whatnot )
-doesn't support the mantle API (see amd section for what it is)
AMD:
+cheaper
+better compute performance
+overclock well
+this mantle API, which right now is unquantifiable, once it's used in some games we will be able to judge it until then we really don't know if it's the best thing since sliced bread or a fart in a bag or anywhere in between
+amd have been working on making their crossfire drivers better
- (and this is my biggest gripe, drivers aside): no viable AA solution to make use of the performance in older games or less demanding games or the average modern game
So I think their higher end gpus (7970ghz and up) are only an option for those with 120hz monitors or multiple monitor set ups (where you have a real use for that performance)
-drivers have been really bad from 2010-2013, it has been better in the past 6 months but it's way too soon to tell if that is just a statistical anomaly or not, I have been soured on their drivers, personally.
Other people who play different games may have had a better experience
-missing the proprietary stuff that nvidia has like physx and lightboost, also no shadowplay for recording (can't remember if they had an amd alternative right now)
-won't be able to use the g sync monitors (well you can use them but not use the variable refresh rate from g sync)
At the lower-mid end i'd probably recommend amd, even though it's a gamble on drivers imo
If you play a lot of older games,definitely go for nvidia (no real aa support on amd to make them look better, there's only SSAA and the amd version has not worked for me in a lot of games, and the performance cost is huuuuuuuge, too huge for something like a 7850 for example)
Whatever you do ,do not buy a gtx 660ti 2GB, that card is a one off with a crippled memory bus, a bad apple.
At the mid-high end (7970ghz and probably 290) you choose between a better price, or AA support
I wouldn't buy either tbh.... fuck nvidia for overpricing, fuck amd for not having an AA solution (seriously, what the fuck is wrong with them)
At the high end (290x) I don't see the point of this gpu unless you have multiple monitors or a 120hz monitor, and we have no idea what the price will be yet or where the high end nvidia prices are going in the next week, need to wait and see.