Gas powered hedge trimmers are just the same as anything else, you get what you pay for.
If you have a lot of large hedges that will need a powerful tool to trim them then you need to be willing to pay for a heavier duty model that will meet your needs and last.
Many trimmers are fitted with a small 2-stroke engines.
This set up is perfect for those with large lawn or garden and professionals who do professional garden trimming service.
This set up isn't cheap and it can make the trimmer heavy but there is always some sort of trade off between price/reliability and weight.
Go to a store and pick up one or two models, if you find that you are unable to pick them up comfortably then you know that you need to look at electric models which are lighter in general.
While weight shouldn't be the only thing that affects the choices you make when looking at hedge trimmers it is important that you are able to handle the garden tool you buy easily or else you will just put of the job of trimming the hedges forever.
The type of hedges you have should also be taken into account, if your hedges are all short and easy to reach while standing with your trimmer in hand then you will be OK with a standard model.
However if your hedges are tall and impossible to reach while standing on the ground then you need to consider buying a pole trimmer.
They come in various lengths and allow you to reach hedge tops and sides that are far above your normal reach.
Buying a pole trimmer is far better than having to cut your hedges while teetering on top of a step ladder or on top of an upturned garden bucket.