The Greenworks 25" 60V mower with it's dual blade and auto switching dual battery features over complicate the mower.
It is a single motor driving a gearbox of some sort that keeps the overlapping blades timed so they don't hit each other. Like everything now a days, it is likely a sealed no maintenance gearbox so I'd be concerned with this failing prematurely.
In the description they state 25" cut, but the pictures state 25" deck. All the Greenworks made 21" mowers are a 21" deck with a 20" long blade / cutting width, so is this dual blade mower really a 25" cut or not ??
I just bought the Kobalt KMP 6080-06 80V Self Propelled on clearance at Lowes for $497.17 last Friday. It has a different thumb operated Self Propel button vs. the Masterforce more common Bale Lever like my 40V Greenworks and my old Lawn-Boys have. I really thought this thumb actuated SP button might be irritating considering I've had bale actuation for 21 years, but instead I adapted to it rather quickly and it does not bother me a bit ... it almost feels more natural and maybe even better than the bale lever since the way the handle is formed both your thumbs are right there anyway.
I'd recommend either this Kobalt mower or the Masterforce as they are simpler than the 25" 60V GW. The Kobalt has a 6Ah battery where the Masterforce has a 5Ah, but if the Greenworks batteries are truly interchangeable with MF (Kobalt & GW are not) this would be a big plus.
The Kobalt is $52 cheaper than the GW 25" 60V and $73/$10 cheaper (before/after 11% rebate) than the Masterforce, so there is that too
The blades for the 21" deck mowers are more readily available too. Both my 40V GW and the 80V Kobalt use the same blade and I'd assume it would be the same blade on the Masterforce.
Lowes stores usually keep this blade on their shelves:
.https://www.lowes.com/pd/Kobalt-20-in-Multipurpose-Push-Lawn-Mower-Blade/1000178401
Lowes states it is for 20" mowers, but this is wrong as it is a 20" blade for 21" mowers (GW p/n GLB333041179 is stamped on it).
There have also been generic Greenworks 80V batteries out there for a while and you can get them in both 3Ah (short) and 6Ah (long) sizes. The largest genuine GW battery is 5Ah.
One of these battery companies in China recently started offering a Kobalt 6Ah version so I snapped one up on ebay yesterday for $140.00+tax. This is less than 40% of the cost of a genuine Kobalt 6Ah battery ($359.00), so figured it is worth a shot.
Doug