ChipFlip
Same brand, same generation, $84 apart. The Sapphire RX 6800 runs $439 used, the Sapphire RX 6800 XT runs $523. Because both come from the same board partner, this is about as clean a same-tier comparison as you'll find on the used market, no cooler mismatch, no revision guesswork.
The core difference is compute units, not architecture
Both cards share the same RDNA2 silicon and the same 16GB of VRAM. What separates them is core count and clock speed, the XT ships with more of both. It's a binned-up version of the same chip family rather than a different generation entirely.
That matters for how you should think about the gap. You're not paying $84 for new features or better efficiency. You're paying for more raw compute inside an identical architecture.
Where the extra compute actually shows up
Higher resolutions and heavier workloads. At 1080p the two cards often land close enough that the difference is hard to notice in practice. Push to 1440p or 4K, or add ray tracing into the mix, and the XT's extra headroom starts to separate the two more clearly.
Same VRAM means the ceiling isn't the issue
Since both ship with 16GB, neither card runs into a memory wall the other doesn't. The performance gap here is pure compute, which makes this an unusually direct "how much horsepower do you actually need" decision rather than a "which one will run out of VRAM first" one.
Bottom line
If you're building for 1440p or higher, the XT's extra compute is worth the $84. If 1080p is your ceiling, the base 6800 gets you 90% of the experience for $84 less.