Which Trimmer or Edger Engine would you rather run.
Four mix
Four Stroke
Two Stroke
Four mix-very eco friendly...weighs only slightly more than a 2 stroke, stihls answer(more like an "f" you) to the small 4 cycle trimmers. generally considered powerful, but reliability has been in question
Four cycle-HEAVY, But powerful motors, the most eco friendly. becoming more and more standard as the EPA pushes back to outlaw 2 strokes by 2020...reliability is questionable on cheaper models. (MTD,Sears,Poulan, ect..)
Two stroke-light weight, gains higher rpms than any four stroke(or four mix) can. can be as powerful as a 4-type, but it is limited to a certain rpm range of efficiency (power band). Hated by anyone who is worried about emissions...but getting better as engineering makes them more efficient.
I use four mix at work, but I will only EVER own a two stroke. you really can't beat em for price, reliability, and weight. I spend too much time tinkering with stihl carbs to consider wanting to own a four mix.