If Piccolo has knowledge beforehand, then he still stomps. He had the power and speed to outpace someone stronger than this Vegeta (Cell) and only got hit due to surprise at this mystery fighter launching a Kamehameha. Piccolo should be more than capable of winning without letting Vegeta tag him, especially when he has such long-range techniques as the Makuhoidan (Hellzone Grenade) to comfortably take down Vegeta from a distance.