Sound wise K712 is definitely very good for general gaming and also competent for competitive gaming.
But comfort wise for long sessions and lots of overall usage AKG's fancy "automatically adjusting" design isn't great:
If you have small, especially downward narrowing head, they can try to slip down easily.
Simply because without manual head band adjustment ear cups rely also on pressure to stay on their place.
Me head is near that limit where they would start creeping down fast.
And there's really thin, eventually wearing down/loosening elastic string as part of their mechanism.
Then price of replacement ear pads is at level where you better be sitting firmly when seeing it.
In constant use ear pads can get dirty in couple years and eventually anyway wear down.
So AKG isn't very wallet friendly in long term.
"Old fashioned" manually adjustable headband is pretty much more adjustable/without faster from normal use wearing down parts.
Beyerdynamic's DT990 would be also relatively similar in overall sound with good above neutral bass for "fun factor", but also other end to balance it/maintain details.
And replacement ear pads are far cheaper than those of AKG.
(nearing two pairs for the price of one AKG pad)
Last autumn released DT900 Pro X is another model in that price level, but it has less bass decreasing fun factor.
And considering comfort in long gaming sessions head band's clamping force is highish 5.3 N, while DT990 Edition's 2.8 N is toward lighter end.
Also weight is in favour of DT990.
Though cable in easily replaceable using mini-XLR connector.
Sennheiser GSX is still grossly overpriced.
While HRTF is really good for fixed/some average head shape based one, audio hardware is at level of generic phone/tablet.
It literally uses cheap integrated DAC/amp chip meant for those.
So output voltage is limited for low current high impedance cans.
And neither it has muscle to deliver that much power if headphones are power hungry.
(AKGs are toward that)
Sound BlasterX G6 has far better audio circuitry and if it were priced similarly to Sennheiser you would be paying closer to £500.
Though for gaming purposes Sound Blaster X3 would have ace in its sleeve:
Head shape customizable HRTF, which can improve positioning accuracy good amount over fixed HRTF.
That upstair's guy simply forgot to standardize human head shape and binaural cues brain is used to processing differ depending on person's head.