Solmanic explained it all succinctly. So you will order one with front and rear diff locks and (unless you live in Oz or Africa) you'll never ever use them, maybe once or twice to see what they do. So maybe you'll settle for a centre diff (fine for 99.9% of situations, certainly in the UK) and when you sell, your prospective buyer will say: "Does it have front and rear diff locks? What? It doesn't?" Because his mates have told him, as above, that you need them and how could you hold your head up at the bar with just a centre diff? The shame of it. The irony is that when the car gets to 20 years old and it's bashed about plenty and you're not going to spoil much taking it seriously off road, that's when the front and rear diff locks might earn their keep. But unless you have money to burn , and some owners do, you may want to try and protect your £60,000+ investment as much as you can by avoiding the most ridiculous of off roading challenges. Or do those specialist off-roading events in someone else's car as I do. And if that's the way you approach your Grenadier ownership, the centre diff is all you need. OK guys, pile in. I can handle it.
