>>214314A hatchet is designed to be used chopping wood.
A tomahawk is sort of a tradeoff between wood chopping, weight and perhaps to be used as a weapon.
I personally choose a hatchet any day of the week. Sometimes an even bigger axe depending on what i'm trying to achieve.
So if weight is a really big deal for you a tomahawk might be your choice. But even then I'd personally look for a small and light axe with a hatchet style head.