Interesting thread (in parts)
So is the bigger tyres likely to put any more strain on the vehicle than you would towing?
Is it likely to have such a vast effect going a little bit bigger? Are these theories or practical evidence based on using these sized tyres from personal experiences?
Strain on the vehicle is a difficult thing to quantify. Bigger tyres and pulling a trailer are different things. And of course what weight of trailer?
Bigger tyres effectively increase your overall gearing. So you will get higher mph per 1000rpm. i.e. you'll be able to cruise at the same speed but with less revs on the engine. The downside is, taller gearing can blunt acceleration and you may find in some situations you don't have the power to pull the gearing successfully or need to drop down where you didn't before.
However in defense to this example. The D2 with either the Td5 or RV8 should have more than enough power in stock form to pull these tyres. And the tyre size is no overly big. It is in fact a standard Defender tyre size. While the Defender and Discovery run different transfer box ratios, there is a well established practice for several decades running a tyre of this size on Range Rover classics, Discovery 1's and Discovery 2's. All of which have similar gearing and kerb weights.
For towing, the main issues are likely to be a slightly taller 1st gear when pulling away, which may result in slightly more clutch slip. Not a problem for a caravan or occasional towing, but if you tow 3 - 3.5 tonne regularly, you might want to consider all options. Also the taller tyres will raise your rear tow hitch, even more so if you combine them with a lift. Without a drop plate or similar, you may find t harder to tow some trailers correctly.
As for the differences going for a bigger tyre. They will give you more clearance, and are in many ways the best for of "lift" you can give a vehicle. You'll increase ride height below the diffs, but also the sills and chassis rails and the front/rear bumpers. Thus improving approach, departure and breakover angles off road.
Larger tyres also tend to roll over the terrain and obstacles better too, especially with a relatively large and heavy vehicle. This isn't to say smaller tyres can't perform, but as a rule a taller tyre is likely to perform better in many situations. A taller tyre while retaining the same rim size will also provide more benefits when you air down, as you have more sidewall and will have a longer footprint.
.... some guys just want to seem interesting while it's not the case and that IMO full of sh*t reply was for no practical use... unless the OP wants to defeat a ''Landcruiser" 
