which is more cpu intensive?

based on the recommended requirements it would be assassins creed by a fairly large margin.

https://www.game-debate.com/games/index.php?g_id=8514&game=Assassins%20Creed:%20Origins

https://www.game-debate.com/games/index.php?g_id=9002&game=Battlefield%201

According to this it would be BF1, but I don't know for sure. I remember when BF1 came out and you could run on lower than what is listed and it would run amazing. It really makes you wonder if EA is getting a kickback from Intel to up the min specs and trick people into upgrading. Check this CPU benchmark out it shows a much much lower cpu like i3 6100t running almost as good as the i5 6600k. Minimum requirement should really be something like an AMD 4xxx or 6xxx series and i3 3xxx or 4xxx which still gets 60fps with good enough gpu.

https://www.techspot.com/review/1267-battlefield-1-benchmarks/page4.html

According to some benchmarks here I would say AC origins is more cpu intensive. Unless origins is just absolutely horribly optimized then it's more intensive. The benchmarks with similar hardware come up much much lower fps.

https://www.pcgamer.com/assassins-creed-origins-performance-guide/

Got a bit off topic there for a minute, hope this helps some.