Why straight shaft is the commercial default
Straight-shaft trimmers reach under fences, shrubs, trailers, and benches better. They also tend to pair with heavier-duty driveline designs and pro-style cutting heads.
Where curved shaft can still make sense
A curved shaft can feel lighter and easier for shorter users doing basic lawn edges. That does not make it bad; it just makes it less ideal for the commercial buyer this site is focused on.
Control beats spec-sheet drama
Reach, line of sight, balance, and the ability to keep the head where you want it matter more than one flashy number. If you are trimming around obstacles, a straight shaft usually pays for itself.
My practical take
For a commercial shortlist, I want straight shaft unless there is a very specific reason not to. If the trimmer will see fences, ditches, beds, or tall grass, straight shaft is the safer recommendation.
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