I'd go electric if I were you- I have a similar ryobi mower, but it's an older model with a wider battery tray and space for two batteries. One slot is just a holder, so the idea is that you simply switch batteries when needed. I love it! A single 5 ah 40v battery lasts me 80% of the mowing time, so if I do the front one day and the back the next, there is no battery switch needed, but it's not a problem at all if I do need to switch.
I also bought it on graigslist, with a compatible weedwacker/brushsaw, as well as a chainsaw. The whole system works well, and I have three batteries- and I think I only spent about $400 total for all 3 tools plus batteries. I am sure the batteries aren't as long lasting as they were originally, but I had no complaints with used tools. And I am VERY happy to not have to store a gas machine, as I have a tiny garage.
That, and gas mowers are absolutely awful as far as emissions, so I am happy to use all electric. CO2 is part of it, but even modern mowers are bad for other pollutants compared to cars that have space for large emissions systems. The low noise level is nice for the neighbors, there are PLENTY of benefits to electric. No oil changes either, or filling up gas cans, which is nice. (Especially as we rarely need to fuel our cars) All the other maintenance is similar, as it is just cleaning and sharpening. Lastly, we went from having gas+corded to a single all electric model, which saved even more space.