Eh, I've done some large-scale Battle levels and you have to kill more enemies and the enemies hit a little harder, but are still easily solo-able. They reward a lot more XP and I got a chest with 5 Amber and 5 X-Potions. A normal leve chest gave me a single Amber.

From what I've seen, you'll get more experience by doing 10 individual standard leves, but it is more time consuming. If you want a large chunk of XP up front with lesser time investment, you can do a large-scale leve.