If Sengoku can use his Daibutsu form, he wins. He felt confident in going after Roger or Shiki alone, so it's safe to say he wasn't far behind Garp. He also got brought up in a statement about the previous generation's legends (by Whitebeard iirc), so he was definitely a top tier in his prime. If limited to his base, it might go either way, to which I'd say Whitebeard wins with extreme-diff due to the potency of his DF attacks, greater range and having easily the greatest durability of any character in the series (bar maybe Kaido).