You will have to think carefully which way to go when considering buying a new lawnmower. Petrol or electric? In all honesty, the main factor influencing the judgment will be the size of your lawn. There may be other things that would sway you one way or the other, but here size probably is important. What are the main things to be borne in mind?
Electric Lawnmowers
Electric lawn mowers are ideal for small to medium sized lawns. They are light, so effortless to push round (they are typically pushed rather than self-drive) and quiet as well. Obtainable in either rotary or cylinder types, they entail far less maintenance than the petrol alternative. Maintenance is even less of an concern with an electric rotary, which aside from cleaning and sharpening are practically maintenance-free.
The main nuisance is the mains cord - you've got to be alert to avoid running over it even on a small lawn. In a big garden the lead can become a real pain in the neck. Just be sure that you are protected by using a circuit-breaker in the mains supply.
One of the best examples of electric rotary mowers is the Bosch Rotak collection. They come in mains-powered (from 32 to 43cm) and rechargeable (from 34 to 43cm) versions.
These cordless mowers of course overcome the chief shortcoming of electric mowers - the mains lead, while retaining the lightness and low maintenance of an electric mower.
The Atco Windsor is a great example of an electric cylinder model that will give you a fine cylinder finish from a mains mower.
Petrol lawnmowers
A petrol lawnmower will invariably be more powerful and more sturdily-built than an electric. Both rotary and cylinder versions are obtainable. Due to their greater weight, they will often be power-driven although some petrol rotaries are push only.
They are more heavily engineered and made, using more metal in their construction, and so will endure heavier use. A quality machine, properly maintained can last a lifetime.
It's important not to overlook the maintenance aspect. You will need to keep your mower well serviced. A petrol cylinder mower will need particularly thorough upkeep if you want to make the most of its durability and reliability. Plan to have your mower serviced yearly - but don't wait until Spring, as everybody will be getting the same idea!
McCulloch is well worth looking at for their collection of petrol rotary mowers - both manual and self-drive versions are available, in sizes from 40 to 53cm.
So there you have it. There are advantages and drawbacks to each category - just think carefully and buy the finest you can afford.