Kryptonian easily. Just stay in the sun for months and become like Superman-Prime.
Anyone choosing Saiyans is a fool. Remember don't just look at Goku or Vegeta but the AVERAGE Saiyan.
Edit:
Kryptonians have the more well rounded powerset, can increase their power more easily than Saiyans and don't require food or oxygen. Saiyans need intense training to increase their power dramatically which would take more time than a Kryptonian needs to power up. Krytonians also age VERY slow. The strongest Kryptonian would destroy the strongest Saiyan,