It doesn't matter how you try and word the outcome remains the same DLSS uses a lower image to create a better-looking image, in theory, 4K its all fake! Sharpening the image to create a fake image that looks like a 4k image its all the same. What does it better remains the question.
The outcome for each of these is to create something better without the performance cost! DLSS is put in place from the performance cost Ray Tracing takes away playing the game at a much lower ref and creating a image that is 4k
AMD takes a lower res and sharpening it up to make you see a better-looking image 4k!
That are both fake! Either way!
4K DLSS is no different than taking a 1440p and upscaling it. It lightly touches the image removing some noise sharpening a bit. However it is proven displays worse image quality than take a 1440p 2x AA image and upscale it to 4K.
FidelityFX and the auto image sharpening is similar to the following example.
Elder Scrolls online, even you max out the settings, the textures do not look that sharp. Settings MIPs to -3 greatly sharpens the image but affects performance in towns (too many different textures), as it is getting processed by the CPU. (Hero Engine). Here we have the same functionality automatically applied on GPU driver level with 0.5% (worst case) perf hit.
(simple example can go technical if needed).
Personally I was pretty underwhelmed with AMD 5700XT performance showcasing until started reading between the lines last couple of days.
First of all the 5700XT resolves issues GCN had in games like Assassin's Creed, Ghost Recon, Witcher 3. To the point is 28%, 22%, 19% respectively faster than a Vega 64 and 2-5% faster than the 2070.
Radeon rep said that "gaming clock" is 1755. Which the clock we would see on the "reference/blower" model when playing games. Stating a max clock 1905, means that something like the Nitro or the RedDevil with 3 fan cooler without tweaking might be sticking to 1900 clock out of the box when gaming, that would push the card making Radeon VII and RTX2080 less than 6% faster. And those two cards are 50% more expensive.