You've probably made your decision by now but I can offer my perspective.
My daily drive is a Trialmaster Diesel and my wife has a Defender L663 110 HSE. She's had it from new and has now racked up 64,000 miles over nearly five years.
We use it regularly for towing a very large trailer with three horses/ 4 ponies and also for days out shooting, so it gets some mild off-roading. It's also used to ferry kids to school, dogs etc. The leather interior has held up well. A bit shiny and signs of wear on the seat edges where you get in and out.
We've had very little in the way of problems. The halo lights have failed twice, the last time out of warrantee, that cost £2500 for a single unit. Service costs are in line with the Grenadier.
It is supremely comfortable, the seats are fully adjustable, heated etc. The engine is quiet, steering accurate and smooth, perhaps too much so. MPG is around 27-29 , maybe more if you're gentle. Tonnes of storage inside and a pleasure to drive long distances. Feel tip top after a 4 hours journey.
So all in, it's been a good car. It's certainly miles better than the Discovery 5 that it replaced.
Why did I get a Grenadier then ? Because I honestly think it will last, it's replacing my run of old defenders, all having being used as intended. It's a huge upgrade in that respect.
The defender is seriously starting to show it's age on the exterior, the bodywork dents and scratches unbelievably easily. The general build quality is below average. Wheel arches have blown off (YES BLOWN OFF), they're stuck on with sticky tape and I'm not kidding.
All of the door seals are perishing and have become tacky to the touch. Deployable tow bar is stuck out, which concerns me as to what the heck is wrong with it (should I even tow with it ?!).
The boot is tiny for such a huge vehicle. Visibility is poor. Illogical infotainment, still not all that familiar with it after five years.
But.... most of all, the after sales care is dismal, it's chaotic and at no time do you feel even remotely special for buying a "Luxury SUV" (not that I want to!) . Also just discovering how horrific it is to own one out of warranty. It will be going pretty soon but I'm not sure what on earth to replace it with. My wife likes the Grenadier but not enough to drive it everyday.
So if it's comfort you're after, get a Defender, if it's longevity, then perhaps a Grenadier, even better a Grenadier MK2 (as and when that may come out) !!
There are two things I would change with the Grenadier.
The Steering (mine is absolutely fine but it's tiresome on longer journey's).
The seats, (the lack of adjustment both to the lumbar and to the rake of the seat is just such a shame).
Not bothered about the "foot rest", in fact I think I would miss it if it wasn't there!!