My previous job was with Lowe's working on the Kobalt product development team. I tested a lot of battery power mowers all brands and sizes, I would recommend a higher watt hour (Voltage x Amp hours = watt hour, best way to compare battery platforms) battery, but to keep it simple the marketing people talk in voltage thus I would look for a 50 volts or higher to get the most gas like performance. Also I would consider the size of your lot, battery power is competitive on <0.5 acre due to run times. Plan to get two batteries these is were battery loses...the cost of the second battery is killer (+$100), I know Kobalt runs a deal where you can get a battery for free with purchase of a mower kit (Kit meaning it comes with a charger and a battery). The reason I say two batteries is my yard is about 0.3 of an acre and when the grass is really grow fast and thick, I need all of one battery and half of the other to get the job done, I was using a 58 volt Echo. That's kinda the basics of battery power mowers.
Now for a head to head comparison...I used the 58v Echo for a whole grass cutting season and I used the newest Honda for a whole season. What I discover was, bagging is night and day, gas is better hands down. If you just mulch or side discharge they are the same, you may have to slow in the thick spots with the battery but your overall time between the two is comparable.
FYI, when you buy any new (gas or battery) mower sharpen the blade right out of the box...the mower stores do this if you buy a commercial grade mower. The blades are dullish due to safety concern during unboxing.
Hope that helps.