SSJ4 Vegito

Do you mean Perfect Cell (At the level he first fought SSJ2 Gohan at) if so then Cell would win. Since Piccolo in the Cell Games, was still standing against the Cell Juniors I'd say he would be able to give some resistence to Vegeta and Trunks from that time.
I believe Piccolo trained because, he always trains even in peace times during the break between the Freeza Saga and the Trunks Saga Gohan asked him if he was still training and Piccolo said he was, people seem to get the idea that Kami being inside him made him not want to train. However Piccolo in the Buu Saga shows no signs of being any different (Personality-wise anyway). Piccolo didn't train like a maniac like Goku or Vegeta. However he probably just got strong enough for there to be a noticable difference, so I'd say he's most likely on even terms with a Cell Junior. Then another 10 years which I see no reason why he wouldn't train since nothing indicates that he didn't and everything about Piccolo's personality says that he did. So I'd say without his weights Piccolo would probably be around Perfect Cell (Fighting Goku) not higher than that. So I'd say Cell wins, if he's at Full Power.