This is a very difficult question to answer decisively. Clearly the commitment to revenge of both of these characters result in their deaths, which is obviously a very negative outcome. However, my own impression is that Laertes has been affected more negatively by his commitment to revenge, but this is because he is used and abused by Claudius, who seems to manipulate so many others during the play. Hamlet at least remains pure and true to his own commitment of revenge and is not used by others for their own ends.
Laertes, as he lies dying in Act V scene 2, has to face up to the fact that his love for his sister and father has been twisted and abused by Claudius for his own ends, and accepts that he is justly killed by his own stratagem. Note what he says in response to Hamlet's question of where is the treachery and villainy that has resulted in his mother's death:
It is here Hamlet. Hamlet, thou art slain,
No medicine in the world can do thee good.
In thee, there is not half an hour of life;
The treacherous instrument is in thy hand,
Unbated and envenom'd: the foul practice
Hath turn'd itself on me. Lo, here I lie,
Never to rise again: thy mother's poison'd:
I can no more, the King, the King's to blame.
Thus we can see from this deathbed confession that Laertes is the one who has been impacted more negatively by his commitment to revenge than Hamlet has. He has allowed his revenge to lead him to become embroiled in the treachery and stratagems of Claudius, involving him in the deaths of others, whereas Hamlet at least remains pure and unsullied in his own commitment to revenge.