Ofcourse Ultimate Shenron (Red Shenron) ! Becouse he can Grant any wish like if u wish tht "Plz Kill Goku" then গোকু will be Died ! This kind of can't be Granted দ্বারা Shenron অথবা Pornga ! So tht's why Ultimate Shenron (Red Shenron) is Stronger ;-) !!