I will use both. If I know I will be able to have good isolation, I will use monitors. If I don't know or will not have good isolation, I will use cans.
For the monitors, I use Audix PH5's. They are a small, lightweight, inexpensive and suprisingly awesome monitor especially given their very reasonable price. They are powered and can be purchased with a carrying bag for around $250. Will they hit 40 Hz? No, but I wouldn't want to carry the monitors and amps around necessary to do so.
As for the headphones, I use a variety of the K240's from AKG and a decent headphone amp.