Battery operated ones now are so much better than previous electrical lawn equipment. I purchased a kobalt trimmer from lowe's and am very pleased with its performance, 100x stronger than the previous corded piece of shit I had. But yeah, not all lithium batteries are the same, check the volts. I went with the kobalt because they too have interchangeable batteries. When I went back to buy a blower they had a black and decker one much cheaper than the kobalt so I thought I'd give it a shot. Thing was about as effective as a hair dryer. Returned it and got the kobalt, which still doesn't seem the blowers have advanced as much as the trimmers have, but it at least gets the job done.
Ryobi, I'm assuming you're getting from the depot of homes, so try it out and if you don't like it return it. Actually just did a quick google search, seems ryobi has 18, 24, and 40v trimmers. Do yourself a favor and just jump into the 40v trimmer, its pretty close to gas powered, the other ones you'll definitely notice a big drop off.
Oh and can verify the 40v trimmers will cut through the fucking vining new orleans st aug grass, the other ones won't without at least a few passes.