We shouldn't classify those as pos. or neg. because every single person might have different oppinion on how much they put ws.
This is my oppinion, but ワロスｗｗｗｗｗｗｗｗ seems more frank and used by the youngers, while ワロタｗ seems just more arkward in this community. The more ws they use, the more they seem to be trying to enjoy to me.
But this is just my thought.