deadpool all the way, now let me tell you why, aside from being one of the funniest superheros out there bar none(loved that scene where he was having a conversation with himself admiring a rich dudes house, but then pies up with "yeah but dos he have a chair made of C4?" fell over laughing after that) hes just plain awesome and outclasses deathstroke , hes an expert in multiple forms of martial arts, an expert swordsman and marksman. It has also been discussed that, while his psychosis and dissociative identity disorder is a handicap, it is also one of his greatest attributes as it makes him an extremely unpredictable opponent. Taskmaster (who has photo-reflexive memory which allows him to copy any one's fighting skills by observation, thus making him their equal in battle) was unable to defeat Deadpool due to his chaotic and improvised fighting style, meaning the man whose power is to copy your every move and beat you to death with your own fighting technique cant overcome the merc with a mouth. his healing factor outclass wolverines and perhaps even rivals that of the hulks. he has knowledge of the 4th wall which aside from being amusing as all hell gives him a tactical advantage if he could ever figure out how to use it
simply put deadpools the better "hero" (and i use that term rather loosely)he may not seem as badass as Slade but that's part of his charm he plays the fool but can kill you six ways to Sunday and then go out for chimichangas without breaking a sweat.