Ive been running the sthil kombi for 6 years, I think my original power head is on its way out,KM110. I bought another km110 at the end of last year and last week I bought the 2stroke homewoners head.
I dont know anything about the echo pas. I thought my km 110 should have lasted more than 6 years <it is still running> . I dont know what attachment echo offers eighter.
I will say the sthil is super easy to change attachments and the attachments are all well worth the money and hold up extremely well.
Im kinda of locked into sthil because I have so many attachments.
If the echo is 2 stroke Id lean towards echo, otherwise which ever one seems more balance to ypu is the one Id choose. Sthil 4 strokes are supposed to be the lightest 4 strokes in the industry.
Parts for sthil seem to be somewhat reasonable priced and not that hard to get, but they are almost all "dealer only"