Sharingan purley for the muscle memory from sight aspect. Id love to bee able to observe someething once and instantly replicate the action without flaw.
if i could have all the Mangekyou sharingan's abilities(Susanoo, Tsukyyomi, Kamui, Amaterasu, Kotoamatsukami) in a Mangekyou without side effects then Sharingan but if not then i would Choose the Rinnegan