Self-propelled lawn mowers come in models with rear wheels that deliver the power and models with front wheels that deliver the power. If the rear wheels deliver the power, they push the mower; if front wheels deliver the power, they pull the mower. Which model you choose depends on the size of your lawn, whether it is flat or has hills, and whether you want a bag to catch the cut grass or don't mind raking it.
Mowers with Bags
If you want a mower with a bag to catch the grass, choose a model powered by the rear wheels. The weight of cut grass collecting in the bags can cause the front wheels to lift off the ground; if the front wheels supply the power, you lose traction. You want the weight in the rear where the power is; that will give you better traction.
If your mower is pulled by the front wheels and you want to guide it around a sharp curve, tree or flower bed, you might have to push down on the back of the mower to lift the front wheels off the ground. The front wheels are not moving in a model propelled from the rear, which makes negotiating sharp turns easier.
Height of Grass
If you are less than diligent about cutting the grass, you likely should choose a mower powered by the rear wheels. Rear models generally have larger wheels and can give the mower a boost or push if you get stalled while cutting tall grass.
Nature of Terrain
Front-propelled mowers are good for a flat lawn. If your lawn is hilly, you probably should choose a rear-wheel drive in which the weight is above the wheels supplying the power. Front wheels might lift off the ground and spin when the mower is negotiating inclines.
Whether your mower is powered by front or rear wheels, choose a model that matches your walking pace. Mowers that are powered by the rear wheels sometimes have a mulching option that is important to some gardeners. R. L. House, a Christian-based information service, says that rear-wheel mowers are less likely to damage your lawn.