Far Cry 5 is definitely the easier of the two to run, especially if you are shooting for high framerates. AC: Odyssey like AC: Origins is insanely CPU heavy and staying at 60FPS or higher can be difficult without a fairly high end CPU. As for which to get, guess it depends if you want an open world FPS or an RPG that resembles Witcher 3 except set in ancient Greece. Whether you'd get good performance in Odyssey would depend on your system specs.