A pointless comparison because
1. Nobody buys a R9-6900H + 3080 high-performance laptop to use the iGPU.
2. R7-6800U (Radeon 680M) ultrabooks cost >1500 USD, at which point you might as well buy a 1000 USD 13-14" 3050Ti ultrabook.
3. Whereas, i7-1255U (XE 96) ultrabooks start at 600 USD, so it can be go into affordable low-end lineups e.g. HP Pavilion, Lenovo Ideapad 3/5, Acer Aspire, Asus VivoBook, etc.
Unlike the supply limited 6800U which is exclusive to only certain extremely high-end lineups.
So multiple price range and easy availability are the biggest advantages of Intel XE graphics over AMD 680M.
4. Upcoming Nvidia MX570 graphics will equal or outperform 680M in most professional apps for a fraction of the price.
This is why I don't understand all this "reviewer" hype around RDNA2 mobile graphics. The tech itself is great, but price point is a complete miss.