I'm not sure this question is actually the logical counter to my question; I've never claimed the Gren is "better" full stop. For me, it's always a question of better for whom?
If you want a car to take to work and occasionally do off road, you're spoiled for choice; there's dozens of options on the market today to choose from. The Grenadier is likely not better for this buyer, and I have no doubt they would get a few hundred thousand trouble free kilometers at least from most X3s, Supras, or Cayennes. So sure, I'll vouch for those vehicles - they look super fun! The vast majority of people don't do the kind of thing the Grenadier is designed for, and would be really well served by any of those models you mentioned.
If you want a car that is available globally, can handle a lot of load for it's size, and has a design that has been proven (ladder frame, solid axles, engine that engines using dead dinosaurs) and therefore familiar to mechanics all over the world for about 80 years now -- which is what I want -- the Grenadier is the front runner based on what we can see of the design. Execution of that design will take a couple of years to really see - proof of the pudding is in the eating, after all! And you are right to point to the LC300 and the New Defender alongside it in terms of capacity/capability, but the Gren edges out the New Defender for sure for my use case. It's certainly is a viable alternative to the LC300 for a lot of people -- I don't know enough about that platform's design to say much about it -- but the Gren is for sure better than an LC300 for me, because I cannot get an LC300 here, whereas it looks like I will be able to get a Gren.
The New Defender is an exceptional vehicle and I'd have one as a DD in a heartbeat -- I actually do agree with you about modern rigs in general, and would rock the Bronco or Tahoe or any other modern vehicle as a daily driver/occasional recreation 4x4 without concerns. I travel with lots of people so I need high payload, but I also like a small footprint which means my choices are limited. But I have questions about it that make me hesitate on buying one for my adventure use when the Grenadier is around the corner and represents a very different answer to those questions.
For instance, what happens if you crack a control arm on the New Defender? They are pretty stout, but metal fatigues over time and I'd be curious how these control arms hold up after 150,000 kms of washboard (though we won't know how robust and work-hardening resistant these parts are for a few years still). Aluminum welding is pretty specialized and can be hard to find someone qualified to do it, even in North America -- the further away from NA you get, the fewer TIG welders you shall see! On the other hand, what happens on the Grenadier if something on an axle cracks? You can two batteries, two sets of jumper cables, and a stick from an arc welder -- the kind of stick that every farmer in the world has a box or two of -- and you patch it. You can even grab scrap metal and bridge it alongside the crack to reinforce it, and there's probably a few buckets of suitable scrap on every farm in the world right next to the welding rods.
What happens if you are tackling a tricky bit of track, so you kill the motor of your New Defender for a water break while you assess your situation, and then you get back in and start it up again only to find it's decided to do an Over The Air update and thus won't start?
You might be stuck with a non-running vehicle for at least a few hours and I've read of others that have gone longer. What happens if the Grenadier attempts to do an Over the Air update? Well, it cannot, because there's nothing in it that needs that.
What happens if you are on a global tour and your New Defender
gets confused about the engine temperature and causes you to think you are in manual mode, prompting you to slow right down and limp the vehicle home? If you are on your first day of your tour, no problem, just limp it home or to your local dealer. The fix is easy for an apparently common problem, but it requires special software to do it that only dealerships have. But what happens if you are on day 300 of that same journey, en route up the Skeleton Coast and about to cross the border into Angola from Namibia when this happens? You are "limping" your rig with an phantom overheating issue at least a thousand kilometers to get to a place that can update the software. What happens if the Grenadier starts overheating? You check the radiator cap, fluid levels, swap out the thermostat, or seek out leaks in the system, or maybe crack an egg into the radiator -- but you don't need a laptop with proprietary software to get things sorted, and the repair and diagnosis process is substantively similar to the process that has been used in automobiles for nearly a century, so if you do get a bit stuck, odds are good someone will know a thing or two to help you.
Everything else - payload, approach and departure, wading depth -- those are all similar enough for it to be a wash. But the above questions speak to how the tool is actually designed to function, and there's plenty of info that suggests for some people (the minority of 4x4 owners, to be sure), the design of the Grenadier suggests it will likely result in less headaches in the middle of nowhere than the design of the New Defender for users like me.
Anyway as I said -- I'm not sure it's exactly an accurate counterpoint to my question -- there is loads of evidence that can be looked at, discussed, and weighed by the purchaser to decide what vehicle is best for his or her use case. But I have not seen any examples or evidence is out there that suggest the B58/ZF combo is not suitable for a 4x4 like the Grenadier, other than comments online about "it's complex" or "I'm not a fan of the BMW motor" or "They shoulda put an LS in it..." -- but
why do folks think these things? Are B58s known to eat camshafts? Do they have hotspots in the block that are known to warp? Do they blow out head gaskets like they are on a 4 for 1 sale at NAPA? Are BMWs with the B58 constantly being rated poorly for reliability by owners? What reasons are there to doubt the powerplant at this point? And what of the ZF? Are they known for failures? What about the ZF makes it unsuitable for the Gren...given the New Defender is a similarly weighted vehicle with a ZF transmission and nobody seems concerned about that? Or the one in the Ram TRX, or the one in the Supra, or the one in the Rolls Royce Phantoms, or the...you get the idea.