well, the only real problem with the doctor is that he is a total pacifist. he makes a point of never actually attacking any of his enemies, opting instead for using his brains to ruin their plans. but in the dark forest, there are no plans. it would simply be a case of the doctor trying to 'avoid' all the werewolves, giant spiders and other sch monsters, many of wich are considerably faster than him, a problem he never seems to face when fighting cybermen or daleks.
harry, on the other hand, would be happy to use his spells to defend himself from the hordes of enemies the doctor usually faces. harry could survive, no question.
"he is a total pacifist"
"he... never actually attack[s] any of his enemies"
He destroyed his own planet in the Time War. He wiped out the Silence by making humans kill them. He arranged for a missile to be fired into Downing Street, killing the Slitheen. He blew up a Cyber-fleet.
He is very capable of violence, especially when pushed.
It is only the recent incarnations of the Doctor that are so adverse to violence. Until RTD re-booted the series, nothing said the Doctor could not resort to violence. Granted, he DOES try to avoid it, but in some of the older series, if it was required, he would use it.
So, I think they would both survive. The Doctor could easily use his resourcefulness to survive the forest, and Harry could use his spells to fend off the aliens.
Well... the sonic can't do wood. :)
Creatures wise though, the Doctor would be able to handle it definitely. I bet he'd have a lot of fun too.
As for Harry, it depends how magic affects alien weapons e.g. electric things don't work around magic. But I think he has the skill to fight some aliens off.
well, no it doesnt. simple. what would make ou think that either of those things would happen?
my original post is the only one that gives good reasons here.