As per stat-wise, Saiyans would be the best race at Super Saiyan Blue Kaioken x10 (Current saiyan's peak transformation) you would have +750 points added to your base stats which supercedes any race's transformation. Heck, a Super Saiyan God is already overkill because it surpasses or is slightly on par with many of the other race's God or Max level transformation. The worst race would be the Majins at their peak transformation stats bonus is +160 which is nothing compared of that to a Super Saiyan God or Super Saiyan Blue.
But honestly, all of these stats are BS and it depends on what you mainly focus on your stats such as Ki Max, Health Max, Melee Resistance and how your fighting styles compare to others. A superior fighter will simply beat another player.