If the umbilical cord thing required for an electric leaf blower won't work in your yard, gas is the way to go. Most of these gas leaf blowers are powered by a two stroke engine and with power calculated in cubic centimeters. The higher the cc the more powerful, starting at around 20 cc and going up over 60. If you have under a half an acre with a couple of leaf raining trees, a 30 cc engine will be powerful enough for you. When looking at anything larger, go for 50 cc or more.
There are three formats for the gas leaf blower.
The handheld version is your option for a small to medium sized landscape where an electrical machine is not practical due to distance from an outlet or major yard obstacles. The initial price ranges from $75 to over $200 plus yearly maintenance costs (including gas). Consider the starting mechanism as well. Like lawnmowers, some leaf blowers have pull start ignitions that can be recalcitrant on cold mornings or hot afternoons. The bother of filling the gas tank may also leave you longing for electric.
These can be heavy dudes as well. Consider the heft when purchasing.
As for the noise factor, the gas powered leaf blowers tend to be noisier than the electric. Unfortunately, this is an important consideration and more than annoying neighbors, you may be breaking the law if your town or city has a noise standard that your leaf blower exceeds.
The gas powered leaf blower is heavier than the electric. This becomes important when you clock in the time it takes to clear your yard. Too heavy a machine and you could experience fatigue and an overwhelming desire to stay inside watching the football game while the leaves stay outside on the ground and the blower stays in the garage collecting dust.
If you find the handheld gas version is too heavy and cumbersome for you, look at the gas powered backpack leaf blower. If you have over half an acre of clearing with some heavy duty debris such as twigs and bark, this may be the best option for you. This machine comes equipped with a backpack apparatus to take the load off your hands and arms so you can work longer with less fatigue. Unfortunately, they come at a three to four hundred dollar price tag and have the same maintenance costs and labor as the gas powered handheld. The machine is closer to your precious ear drums making noise an even more important factor. These models are not as versatile as the handhelds, as there is no possible way to vacuum up the debris - only blow it. If you opt for a backpack leaf blower make sure there is hefty back and shoulder padding along with adjustable straps and a handle to carry the machine to the leaves and back to storage.
If your wallet can handle the strain, and your heart beats faster at the word "power", at least take a look at the gas wheeled models. They can wallop the daylights out of your leaves with over 1000 cubic feet per centimeter rating and all you have to do is push the machine like a lawnmower. But add in all the down sides of gas when it comes to maintenance, the fact that it takes up way more space in your garage, and the ever-present noise factor and you may want to think twice before purchasing the wheeled model. If you have a large yard, however, this may be a great option.