Goodmorning. Merry Christmas.
I need some advice. I can’t decide between the 4080 and 7900 XTX for my new build. The 4080 is 200 euro more, but need some more psu power too. I’m going to use my QLED 75 inch 4K. So i’m a bit worried about the VRAM. Although I play also other games where raytracing is better and the 4080 is more power efficient.
I’m pairing it with a 7800X3D. Already ordered the 4080, but it hasn’t shipped yet so I can still swap it for the 7900 XTX.
Thanks
Merry Christmas 
If I were you I would wait for the 4080 Super, also the 7900XTX could soon benefit from FSR3 frame generation (there is already a mod that allows it) and may give you better value for money than the RTX 4080.
Of course if also ray tracing is important for you, the RTX is better overall.
Both of these have gotta be good!!! - From what I’ve heard elsewhere RTX Nvidia cards are smoother than AMD - At least of RX 6000 vs RTX 3000 cards.
Raytracing is lots better on Nvidia - But AMD have improved from 6000 series to 7000 series.
My 2 cents is that Raytracing is early on it its life cycle.
7900XTX has the 24 GB VRAM! - RTX 4080 only has 16 - But maybe RTX 4070 / 4080 Super will get more? - We’ll soon find out! - Very soon unless release gets put back for some reason.
Usually game fans / computer enthusiasts will collect GPU’s over time - Both AMD & Nvidia but they are sure expensive.
Don’t forget AMD RX 7900 XT as these have 20 GB VRAM.
I’m hoping that MSFS 2024 will be optimized well enough for multi-threaded workloads that a top of the line GPU such as RTX 4090 isn’t needed.
Naturally RTX 4090 will always be wanted but if it isn’t needed to get “good” results more folks here will be happy.
RTX 4070 is quite good and cheaper
RX 7800 XT is AMD’s lower card similar to RX 6800 (non XT)
On Youtube the other day I saw a video from the “Flight Sim Guy” with an AMD 7900 XT and he claimed it was as good as his RTX 3090 - So this can’t be bad - But I’m not sure how good the VR would be
The mod is for FSR3 frame gen to work on Nvidia RTX 3000/2000 series gpu’s. There has been a FSR3 frame gen preview driver availble for several months for AMD 7000 and 6000 series gpu’s and it works very well (been using it with my RX 7900 XTX).
From what I can tell, it appears AMD will be releasing FSR3 frame gen within the next month or two as part of its WHQL driver.
I never compare eg GPU that i CAN have (4080 vs 7900XTX), i compare what i HAVE for example (GTX 1080 vs RTX 4070) what i had before. In my situation i had a “winner” either way.
I went with a 4080 a year ago because no frame generation for AMD cards was on the horizon. Today I would go for the 7900XTX due to the bigger VRAM. I max out my 16GB easily on big hubs and this already with 1440p. So for 4K, the 24GB VRAM will be a plus for sure. Or you wait until the final specs of the 4080 Super are available, might come with 20GB VRAM.
Are you running 4K HDR10 Fenix / PMDG at big hubs? How is the driver frame generation? I can’t find many people using it except you. I’m a bit worried it doesn’t work that well as DLSS 3.5 FG. On the other side i’m a bit worried about the 16gb vram.
I’ve always run the sim at 4k HDR10 without issue going back several years with my old RX6800. I do not run Fenix/PMDG however I think the additional stress there is more with the cpu, not the gpu. I do fly the A320 Neo, Longitude, F/A 18 out of KDFW, KJFK, EGLL, and KLAX with FSLTL without issues with frame gen with either FSR2 upscaling or TAA.
They are out there it’s just that you don’t see a maddening number of posts that it’s not working. 
. While it’s not perfect, there has been a steady progression of improvement over the last several months. Check out YouTube as there are a lot of videos on the AMD frame gen driver. The fact that AMD have just merged the latest WHQL v23.12.1 driver fixes into the preview driver tells me they are close to general releasing frame gen as part of their WHQL driver.
If you go with th 7900 XTX and there are any remaining issues with frame gen, they can always be fixed by AMD in the driver. With the 4080, you will have no recourse to increase the 16gig vram short of selling it 
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I’m running in 4080 mobile happy with the performance with settings on ultra. I highly recommend.