If you purchase the new 7.5Ah kit, I don't think the Greenworks can hold up. There is no official comparison. I like the ease, look and performance of the EGO mower, and so do official lawn tool reviewers. Usually even if a lower run time with the smaller 4.0Ah battery, the EGO ends up on top of all battery powered mowers. It's a fantastic machine Bill.
I'm not just saying it because I own one. I own different brand devices that I like just fine. A Greenworks tiller, it's great. A Black and Decker hedge trimmer that has been great for 3 years. My EGO tools that I'm thrilled with are the mower, blower, chainsaw and 15" weed eater. Whomever takes the leap and puts out a battery powered dedicated edger, I'll probably break down and buy it.
I don't particularly like having multiple brand batteries. It makes for a charger and battery mess. MY Ryobi hand tools, love them, my Hoover vacuum cleaner. That makes 5 different chargers and battery types that are not compatible with each other.
Put what I said above when making your purchase. If you like EGO, consider going with that ecosystem for most of your tools. Their battery performance/design is second to none. Though I am not thrilled with Apple, all of our phones and tablets are Apple, so that we have one charger and cord design. It is so much easier. Don't be like me and have this mess to deal with.