It's the cache. Simple answer is the cache. That makes a big difference for gaming.
It makes less difference for other tasks, though, while the incredible core count of the 7950x helps with a lot of things. Right now, getting a 7800x3d is tough anyway. I just bought most of a new computer and went for a 9950x which is actually not much more expensive.
I wouldn't worry about it. If you're determined that gaming performance is the only thing that matters (or that the core count does you no good--either of these things is certainly reasonable) i would still wait anyway for the 9800x3d. That's probably going to be out by the end of the year and likely will be a step up... or at least obtainable near MSRP.
Basically, don't worry about it.