totaly depends on what battery you want...the lithium batterys are the best as they are lighter and easy to fit in a pocket...
the scope mounted lamps are ok but i find you have to point the rifle at what your looking at so you could be pointing the rifle at somthing that is not your quarry so you need to be extra carefull..
i would get a 170 handheld light force lamp, and if it was for my scope i have a 140 lightforce lamp...and pick up a extra bulb for each lamp as spare to put in your kit bag...plus a red and amber filter for each lamp...amber for foxes and red for rabbits..this is what i use but other people use different lamps and colour filters...
i guess alot depends on what your wanting to lamp for and what rifle...