[Gustoo]

Necro is fast solo
Cleric is slow solo

Both can solo but cleric needs to med after using basically 100% of mana to kill a single mob.

Both are fine in groups.

Necro can really kill monsters more efficiently.

What do you want to do more?

If you expect to play for shorter bursts and not neccesarily get a good dungeon team going, I would go necro and be more productive during your play time.

These are my favorite classes in the game, maybe.