Cylinder lawn mowers are gentle to your lawn. They cut the grass like a pair of scissors, which improves your grass health. Because the mower runs on human muscles, there is no engine noise or emissions. The manual cylinder mower is also cheaper in maintenance because there's not much to maintain, apart from washing off excess grass clippings.
Is there a catch? If your lawn is relatively small and even, the cylinder mower might be perfect for you and your lawn. Although the mower is relatively lightweight, it still offers you a healthy exercise. Is your lawn medium to large, hilly or uneven, you will probably be happier with the power of a petrol or electric lawn mower.