try the drill and see how long it lasts, then, if you think you need more, then buy a power head. i'd buy icegator if i needed/wanted a power head.
plenty of stories how the drill works fine for most. if you are going over 6 inch holes, then a power head would be best.
i take some pressure off of my lazer augers while driling so they aren't taking as much ice out per revolution and more so towards the end of the hole. makes it more like a shaver auger and not put as much resistance on the drill.
i like to drill lots of holes if the bite is slow and check the holes with a sonar. cold will deplete batteries so use them while they are warm or keep them warm. it takes a while for the cold to deplete them tho.