If you can afford it......go Stihl. The comsumer warranty is a ridiculous five years. They just replaced mine with a brand new one due to a carb issue....after 4 years of use.
While mine was in the shop for the months, I used my neighbors 4 stroke Craftsman. The thing is is not that heavy at all and has a lot of power. It edged dirt and can cut a trench. Use their special heavy duty red speed load stips and I did my entire property on 2 strings (full acer, 300' of fence; 288' of sidewalk; house, patio; 6 car driveway.) Only thing I hate is the curved shaft. Straight shaft is better in my opinion as it prevents less bending.
-In God we trust. All others, put your hands on the car and don't move.