if your in town, trimming around house and like a "curved shaft" trimmer more likely good enough and easier for you. and small engine size most likely ok for you as well.
if your living out of town on a farm or on a few acres. were every now and then, you need to weed whack a few tall weeds. then you will want a "straight shaft" and you may want a bigger engine, more so for cutting larger weeds
if you need to use a "brush cutter" metal saw blade vs string. to cut weeds up. you will want a straight shaft trimmer
straight shaft trimmers = solid rod inside of them
curved shaft trimmers = a flex shaft inside of them. and those flex shafts do not hold up to the abuse of trying to weed eat tall thick weeds.
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buy the "drill starter kit" = something you place into a battery operated or corded drill. and then place into trimmer engine. and you just pull trigger on drill to get things started. other words the drill bit = slip clutch, so once trimmer gets started the drill nor the trimmer engine gets messed up.
ya on a new trimmer they should be pretty easy to start. but when your rear is dragging across the dirt, and you pull and pull and nothing happens. it is nice to just use the "drill starter kit" and within a few moments voom voom voom, and away you go. ya it may take a few seconds for drill starter kit to get trimmer engine going. but sure beats pulling the rope till ya dead tired and need a break before you start trimming.
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make sure it is easy to fill with fuel errr gas/oil mixture
make sure it is easy to clean air filter.
make sure it comes with a tool or easy way to stick screw driver into "bump head" and shield. so you can easily remove bump head, and add more string, or get things unstuck inside the bump head.
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ma bought her self a "wead eater on wheels" looks kinda like a push mower, but the front of the deck was chopped off, and instead of a metal blade a push mower would have, it is weed eater string. that thing rolls "extremely easy" up and down and across hills. and very light and easy on the neck, shoulder, back, arms. has large wheels on it. vs a push mower, so going over bumps or ruts in the mud is easier.
the only down sides of weed eater on wheels.
--is it can take longer if you have to weed eat large "wide areas" were the riding lawn mower or zero turn mower not able to cut, a regular weed eater / trimmer you can more quickly move left to right fairly quickly, unlike weed eater on wheels were you have to pull back and forth like a push mower.
--and you may not be able to get into some tight areas, due to size of it like a push mower.
but over all, weed eater on wheels is a nice machine.