The advantage of them is that with a suitable chainsaw garden jobs like chopping wood need not be the back-breaking tasks they usually are.
You would need to do some research and determine which type of chainsaw suits your requirements best. Electric chainsaws are usually cheaper, lighter and are simple to operate. They are relatively quiet.
A petrol garden chainsaw will cost more but will be faster and more powerful. It will last longer too. You can use it anywhere and don't need a power source.
Bear in mind that a chainsaw can be a very dangerous thing unless you know what you are doing. Don't use one without first getting adequate instruction. It is essential that you wear the correct protective clothing at all times including goggles, hard hat and gloves.

With A Chainsaw Garden Work Is Made Easy
Poulan Pro PP3516AVX 16-Inch 35cc 2-Cycle Gas Powered Anti-Vibration Chain Saw