While leves are faster, I also find grinding out a certain item for DoH leves to eliminate some of the grindy feeling.

For instance, yesterday I was taking my culinarian from 20 to 35, leveling off leves that required chamomille and millioncorn. I pretty much grinded out two levels of Botany before I even knew it by harvesting these items until I had a considerable amount of the HQ versions of each. In my mind it seemed to go by much faster since I was focusing on the goal of leveling my culinarian.

So in short, I would use leves to level faster if you can afford the allowances, but also occasionally grind out a level here and there especially if it can yield you usable items for your other crafting classes.