need both, well technically not RT, but you need a better lighting/shadows solution (that UE5 provides) to help bring out the detail in the dense Nanite meshes, or you won't really be seeing the difference.I know people are hyped over RT but for me, the new geometry capabilities and things like Nanite excite me more.
Every generation has a 'look' and I believe the look of this generation will be insane geometric detail.
Horizon:FW already seems to be pushing so much geometry and looks so much better for it.