I have both models and get a huge amount of mowing exercise with them. The larger model has a wonderful automatic ramp up of power when under load. For example, I have a mossy area of lawn that completely stalls out my smaller mower, but doesn't even appreciably affect the larger one.
In addition, if you get the high-lift blade, it will pack your clippings bag really tight before it needs emptied. The high-lift blade seems to pull unwanted seeds and even insects off of the grass. I love it. I recommend an additional battery though.