As other have said, the lockers are Eaton e-lockers. There are things we know about them, and things we do not.
(1) We know that the Eaton e-lockers disengage briefly when you shift from forward to reverse, and vice-versa. This is not ideal for technical driving. Both air lockers (e.g. ARB) and mechanical lockers (e.g. Ox) will stay fully "locked-up" when shifting from forward to reverse (and vice-versa). Depending on how technical the obstacle, the Eaton lockers may exhibit shortcomings with loss of traction. But much will come down to the terrain you drive: if you engage the locker(s), drive forward through an obstacle, and then disengage the locker(s), this problem will not present.
(2) We do not know how readily the Eaton lockers engage in the Grenadier. There is considerable variability in how quickly factory-installed lockers engage. The lockers in the Ram Power Wagon are the slowest to engage, followed by the lockers in the Jeep Wrangler Rubicon; in contrast, the lockers in the new Ford Bronco engage immediately.
(3) The Eaton lockers are actuated electronically; do with that information what you want. Air lockers are dependent on an air compressor, air lines, and in the case of ARB, O-rings that can degrade over time and fail. Mechanical lockers are dependent on a steel cable that can stretch over time and will eventually need adjustment. By far, the mechanical locker is the most robust option, but at present - no mechanical locker for the Grenadier exists.
(4) We do not know if the Carraro axles are compatible with any aftermarket locker currently available (this lack of information is - in my opinion - unacceptable).
(5) We do not know if the aftermarket will develop gears or lockers for the Carraro axles in the Grenadier. The Grenadier is likely to be a low-volume vehicle, so maybe not; or maybe the Grenadier takes off, and someone (ARB?) develops a vehicle-specific locker for it.
(6) We know that Ineos will not retrofit the lockers after the vehicle is produced, so if there is a chance you want them, it is best to order the vehicle spec'd with the lockers. Given the unknowns, your choice may be: order the Eaton lockers from the factory, or never have lockers (unless you replace the axles - see below).
(7) The lockers from Ineos are a better price than what you will pay in the aftermarket - unless you install the aftermarket lockers yourself. But right now, there isn't even an aftermarket option that we know of.
(8) The factory-installed lockers come with a warranty.
(9) Factory lockers will add re-sale value to the vehicle.
Given all the variables, it seems like ordering the Eaton lockers from the factory makes the most sense - unless you are certain it is an option you will never need, and/or the price poses a hardship.
If you do not order the Eaton lockers, and you decide later that you want lockers, maybe there will be some in the aftermarket. If there are no lockers in the aftermarket, and money isn't an obstacle, you can swap in a set of Dynatrac Prorock axles, and you can spec these axles however you choose - they are all handbuilt here in America, and Dynatrac can custom-build to any vehicle. For around $20,000 (plus shipping if you are overseas) you can get:
1. Full-float axles (stronger and easier to work with in the field than the semi-float axles that come in the Grenadier)
2. Whatever gears you want (allowing you to spec the axle for larger tires, should you wish)
3. Whatever lockers you want: e-lockers, air lockers, or mechanical lockers.
EDIT: pricing for Dynatrac axles has probably gone up due to inflation.
