You can run games with insufficient VRAM just fine. Stutter doesn't always appear in reviews and canned benchmarks. But I'm sure the W1zz is right on the money trying to figure that out if the moment arrives. Nvidia can deploy a lot of driver trickery to still provide a decent experience, they've done similar with the 970 for example - all the VRAM related bugs were fixed on that GPU.
Does that all TRULY mean there is enough VRAM though? That is debatable. The real comparison is side by side and careful analysis of frametimes. Gonna be interesting.
trough the years of playing games and following games requirements i have impression that devs decide game requirements and vram in particular either by vga cards available or soon to come (a month or 2 max) on the market or more often just by playing darts.
on my 290x 4gb i've played titles that "required" 6 or even 8gb vram just fine. i've dialed up texture quality above recommended if i didnt liked how the game looked and still hadnt problems because of lack of vram. so judging what is enough based on game requirements is a bit pointless.
set a price range. check what meets your performance requirements. buy the card with highest amount of vram that fit your price and you are good to go. by the time the games look too ugly because you had to lower textures the card would be long dead fps wise.
as for 970 the problems never was in the amount of vram. slow 0.5gb was what caused the problems as it tanked performance very hard. when nivida isolated those 0.5gb with drivers 970s worked fine even with titles that required 4+ gb vram.
on tech level both camps have different approach for solving vram limitation.
nvidia's lossless compression allows them to have lower capacities and bus but to preserve higher performance. so they fit as min as possible memory for bigger margins.
with gnc amd had to throw a lot of memory bandwidth (bus for 7970 was 384bit, 290x was 512bit, fury, vega and vii were 1024bit) to provide enough "fuel" for gpu but it never was enough. from rdna amd have memory bus topped at 256bit which before was for their midrange cards (no doubts 5700xt itself is midrange card) and now with rdna2 even their top tier 6900 has 256bit bus. sure new cash provides higher speeds but still you need to feed this cash with adequate speeds and amd thinks that what was before bus suitable for mid range cards is now enough even for flag ship.
i think 16gb ram in amd's cards is more targeted at feeding the cash (like load all textures in vram so cash can have instant access w/o need of calls from ram/storage) and/or they believe the can have significant performance boost from direct cpu access to vram so they made sure they provide enough vram for devs to play with.
it will be interesting to see if those thing will really help amd
Imagine the outrage if Nvidia did something like that
i dont have to imagine anything. they already did it with hairworks, forced tessellation and gameworks (or wharever it was called) extensions and physx. i dont remember the outrage thou.
now that amd holds consoles and devs has to do optimization for amd's hardware the coin has flipped and nvidia is quite jumpy when something becomes close to take away "performance crown".
a single game announcement is enough to cause... leakages
btw physx is open source for some time now