ChipFlip
The RX 9060 XT is AMD's newer card, and it's priced $25 above the ASUS RX 6600 XT used, $270 against $244.95. For a card two generations newer, that's a small gap. Is it worth paying?
Two generations, one small price gap
Normally a generational jump like this comes with a real price premium attached. Here it doesn't, and that changes the calculation. A $25 difference is close to noise once you factor in shipping and any price movement between now and when you actually buy.
What the newer card actually changes
The 9060 XT brings a newer architecture with better power efficiency and improved ray tracing support over the 6600 XT's older generation. Neither card is built for heavy ray tracing workloads at high settings, so that advantage matters less here than it would on a higher-tier card. Where it does matter is efficiency and driver support going forward, since AMD's newer cards get feature updates the older generation eventually stops receiving.
The case for the older card anyway
$244.95 is still $244.95. If the extra features on the 9060 XT genuinely don't matter for what you're building, that's real money saved for a card that still handles 1080p gaming fine. The 6600 XT also has a longer track record on the used market, more listings, more history to compare against.
Bottom line
At a $25 gap, the newer card is the easy pick for most buyers. The only real reason to go older here is if you've found a 6600 XT priced meaningfully below $244.95, at which point the math flips back the other way.