I think that Doflamingo has a better chance at victory due to having pre-cog + clairvoyance, Mid-low Regenerationn, environmental manipulation via DF awakening, range, and manipulation hax (via parasito).
Pit may have immensely faster travel speed, have more versatility (broken hax as well), and is likely stronger due to being at least capable of generating 80 Gigatons of energy with his strongest attacks (speaking of which, his profile needs to be edited to all 3 of his keys being "Island level+" and "At least Island level+"), but Doflamingo could take attacks from someone who was physically stronger than him after having his internal organs damaged, which should have rendered him incapacitated.
Doflamingo should also be fully capable of intercepting projectiles from Pit with his waves of threads and Kumonosugaki. The only real threat is keeping track of Pit's position due to his MFTL+ traveling speed in flight, but Doflamingo can respond to that more quickly due to pre-cognition, and that he will be surrounding himself with haki-infused threads that can protect him from every direction.
If Pit can land hits on Doflamingo, Doflamingo can recover quite quickly, and keep fighting even if the wounds are near-fatal. Doflamingo does not need to expend much of his stamina while using his awakened attacks, which is an advantage itself. However, if Pit is the one taking blows, it will build up until he is too injured to keep fighting back.
Pit still has a chance to win due to his superior stats and potential hax, but they need to hit, and Doflamingo is capable enough to evade them even without pre-cog, and he would be fully capable of fighting from behind his power. Even if Pit gets through the threads, Doflamingo is formidable enough to defend himself in a hand-to-hand confrontation.
Doflamingo should be capable of winning with high difficulty, though i'm not fully knowledgeable about Pit.