There are both advantages and disadvantages of using electric and gas mowers. If the yard size is small to medium then an electric mover with a cord would be best and is cheaper too, but then cord interference can make it difficult to use due to restrictions on movement.
On the other hand, gas mowers are best as recharging is not needed and there is no cord restrictions but then the gas causes pollution and dangerous from health and environment point of view. The best gas mower is Honda (the vaunted HR215 series), which is cleaner the most than any other gas mowers. There was also a very good electric mower earlier which was Husqvarna rechargeable mower, even though it was very effective but is not very popular in the market due to high cost. A cordless electric mower is also a good option but they are usually expensive. So basically, you can go for the one which suits your needs and is convenient from your point