Walmart has both of these rifles on the shelf for $150. The Gamo is a .177 and the Benjamin is a .22 caliber. Living in a sub division i needed a rifle that was as quiet as possible.
The Gamo is supposed to be 52% quieter than other air rifles. Well it might be 52% quieter than a 30-06. It has very loud crack when you shoot it. Not a whole lot different from a 22 LR. I dont know what there doing to the sound on the TV commercials but it is not the reality. My research stopped right there as theres no way i could use it.
The Benjamin states its nitro piston is 70% quieter than its leading competiters quiet gun. It appears to be true. Even though it is way more powerful then my old pump up gun, the noise is about the same. Its also very accurate. I had to try a couple of different pellets but i found one that will shoot sub 3/4" groups at 25 yards. Plenty good enough for squirrels.

A silencer for an air gun is a good thing.