The best place to chop magic trees is at the Woodcutting Guild, located in the southern part of Great Kourend. Eight magic trees can be found here in very close proximity to a bank.
Depending on levels, players can chop 70-130 magic logs per hour.
Other spots include the courtyard of the Sorcerer's Tower, outside Lletya and outside the Mage Training Arena. However, they will net a significantly lower amount of logs.