For firewood use I've heard the 2159 is better because it has a flat torque curve. Ultimately the 2156 has more power. My uses are strictly for firewood. Biggest trees I like to deal with are 16-20". Mostly just cutting up stuff that is already down. Local dealer has a 2159 in stock and wants $600 which ivthink is a lil steep. Can order a 2156 for $700...