Home Depot has the Milwaukee M18 String Trimmer for $199 today with 9Ah battery and charger.
I have a 4 stroke Stihl. It's good, and it cuts/trims very well. I have used it for 4 years now, and I have had no issues with it at all. Much better than the Homelite POS I had before, but it was quite a bit more $$$.
But the electric trimmers are nice. Quieter and most are lighter. I use one at a relatives home fairly often, and sometimes wish I had one!
If you mostly use string and no attachments, I would strongly consider electric.