I just prefer the way they price their goods. Amd also seems to put a focus more on engineering as best they can over marketing over-hype. Then, as others have said, their products tend to age like wine, whereas Nvidia tends to age like milk. Especially considering their pricing. Add in the difference between freesync and Gysnc, and with the consideration of how OpenGPU is based off of Vulcan, it seems to me like AMD is more interested in parity in the computing engineering realm, instead of profiteering and short term gains like Nvidia and Intel are. To me they seem to be 'the good guys'. I'm willing to bet that they do this because they are so over-shadowed by their competitors, but believe me when I say I would not hesitate to criticize them if they started engaging in unsavory practices.

Going back to what I said before about how their GPU's age well and their development practices, they really seem to be looking farther into the future than either intel or Nvidia in the development space, because they compensate for future opportunities for their consumers that might not yet be available. Hence, they included a lot of 'asynchronous compute engines' in their GCN cards before the technology could really even be utilized by DX in gaming. (This element about them did, however, make them quite useful for bitcoin mining, interestingly enough.)

Nvidia gameworks is another reason why I prefer AMD, because, again, AMD is attempting to take the parity route whilst Nvidia tries to push for exclusivity for the sake of profiteering.