lol...they're basically the same headphone, cosmetics aside. Their 53mm driver may be tuned differently between the two of them, but the difference will be minute since they both use the same magnet and diaphragm membrane material, especially if it's AD700 vs. AD700x. The most notable sonic difference between the AD700 and the AD900x will be the earpads. Thicker earpads give you a better seal, which means better bottom end. The AD non-x earpads are really shallow, which means weaker bottom end. So really, you're looking at a difference of sound signatures. One isn't inherently better than the other, except if you really want some bass. Then again, you'd probably looking at other headphones if you wanted that...
For gaming, they will offer the same benefits...the AD series stages pretty well (main reason why the AD700 is so popular, besides comfort and price), their 53mm driver has a good amount of speed, especially the AD2000/x drivers (not sure on the 1000/x, but they look like the same driver, so it could be a tuning difference), both have a slightly bright sound signature, which makes it easy to pick out certain sounds like gunshots, and the weak bass emphasizes that a bit.
Anyways, I thought I'd share a bit of info on AT's drivers.
The difference between the AD2000 and the AD2000x driver (not the headphone housing the drivers), is the way it's ported in the back. On the back of both drivers there are little holes surrounding it all around, and it's covered by black felt material. If you look at the AD2000x driver, you'll see that holes completely surround the driver. On the older AD2000 driver, two of those holes are covered up by the PCB. That PCB allows the headphone cable to connect to the driver, which allows the audio signal to pass through two little wires underneath the diaphragm membrane to the voice coil. AT placed that PCB right on the driver itself on the AD2000. On the x revision, it seems like the PCB was moved somewhere else, possibly inside the little tunnel where the cable leads to, so that none of the ports are covered up. Maybe, a_recording can take apart his AD1000x to see where it's at, since both the 1kx and the 2kx use the same driver frame. So, what do those uncovered ports do to the sound? Not much. If anything, you'll get slightly better bass performance because there is less restriction (low frequencies have a larger excursion area than higher frequencies, which means that more air is needed/moved when producing lower frequencies), and this is not taking into account the earpad differences between the non x and the x series. When you factor in the earpads, the AD2000x will have better bass performance, both in quantity and in quality, but the quality difference will be negligible. Two covered ports will not drastically change sonic performance, especially if it's tuned to compensate for it.
The driver enclosure that holds the membrane and magnet in place on the AD 1k/2kx is a unibody frame made of metal, with the magnet being inside the frame instead of being exposed like on my AD900 drivers. When you look at the AD1000/2000/x from the outside, you'll see a black bulge in the center of the driver. That's the frame. The magnet is inside that. On my AD900, you can clearly see the magnet, like it was glued on from the outside. It's also thinner and heavier than the lower-tier 53mm driver units. I'm thinking the change in material helps with resonances that may exist with the plastic driver frames, and because they didn't want to skimp out on putting a driver frame comprised of cheap materials on their high-end headphones.
/rant
Y'all can check out Roison Murphy's Overpowered (Seamus Haji Remix). It's one of the few EDM songs that I can listen to without getting tired of it.