Noob friendly? Probably neither.

Mage is a great class if played right. However, as a noob (no offense) you probably won't play it correctly. You have to use your slows/snares/cc wisely while also paying attention to your targets and doing your "rotations". Ice block is okay in "oh shit" moments and you can have some great burst potential. However, if there's a melee on your ass and you can't kite him away, you're pretty much fucked.

On the other hand, i'd recommend a mage to a noob if they were interested in pve, as it's one of the more simple classes to play in pve with a very small rotation.

A warlock has great damage, massive DoTs, great sustainablitity if used correctly, INSANE cc, and different types of pets that give you different abilities. As a noob I do not recommend a warlock, because paying attention to all your cc, pets, DoTs, surviving, and putting out big deeps can be kind of overwhelming.

I mean obviously play what you want to play, but don't expect to pick up one of these classes and hit 2k in the 3s arena any time soon. You need tons of practice with both of these. They're great classes, but a player who knows how to play these classes well and maximize all of their abilities really separates the boys from the men.