Taste. The PROTANK Mini is so far the best thing that has come to me Clearomizern below (there are probably even better;)). The steam is super and especially the taste. Nothing gekokelt ... pure steam.
I use the PROTANK Mini II together with the VAMO V5 battery carrier and Panasonic 3.7V 3400mAh battery. For me an absolute ideal combination.
Tip: Buy! The best you can to get Clearomizer for this money.