I was a bit surprised you rated Ryobi...don't know why. I'll check them out. I had a look in a Bunnings a couple of weeks ago and the amount of machines they had in there was mind boggling!
I've seen Ozito is only rated for light residential use and have also seen a few Ozito cordless trimmers thrown out that look brand new.
I prefer an expensive Makita to Ryobi but it just depends how much you are willing to spend .
Personally I don't have much use for line trimmers, if I can't cut some grass with the mower ,I just buy some weed killer
and give it a spray and it's dead in a couple of weeks.
Bunnings have some reviews but the Makita I've seen there are only 18 volt.
I don't think of those half size trimmers as line trimmers they are just rubbish to me.
Cheers
Max.