Chose the higher cranking amps for the extra power. By the way, if you own a single engine general aviation airplane or know someone who does, you can use a used airplane battery that is no longer adequate for the airplane. Most of these airplanes use 100 to 180 hp engines and require a high-quality battery. While the batteries for small planes are only 225 CCA, the quality of these batteries and the cell density is so superior these batteries cost $300-$400. The benefit is that that airplane batteries are designed to crank 180 HP engines, so when it gets too weak for that, they still have more power than you will ever need for a 20 HP lawn mower. Fortunately, these batteries are physically the same size as most lawn mower batteries ( 7.7 inch L, 5.18 inches W, 6.8 in H., take measurements before you go to the airport). Some are sealed, others require distilled water just like most, older lead-acid batteries. The caps: however, are screw-in and don't leak if the battery is knocked over. They are designed for aerobatics. Lastly, many of these used batteries are NOT returnable so the Airport mechanic, FBO, has to dispose of them. Might just give you one!