i think its sharingan.it can be very useful in combat,although it cant analyse your oponent as well as byakugan.but still it can help in a number of occasions,like distinguishing the oponents real body if he uses a bunshin(clone) technique
I demand to know why the Rinnegan wasn't included in this topic *turns into the HULK* but Sharingan definitely. Base Sharingan by itself is useful with the ability to copy jutsu's and predict opponents movements w/o losing your eyesight. Then it has the upgrades of MS/EMS if your willing to strain your eyes/body for that type of power.
Definately the Sharingan, i mean can the Bakukugan suck people into other deminsions? plus with the sharingan there are different kinds and stages... the bakukugan doesnt change they're all the same...