If you are inexperienced with using a chainsaw it is better to pick a lighter version, since they are easier to handle. Professional users, working full days in the forest, will of course also appreciate a low weight chainsaw.
You should also make sure that your new chainsaw is powerful enough for what your intended use. If you will be doing heavy work, you will need more power and also the right cutting equipment. Most specialised dealers will be able to help you get the right size.