I have the Premier LTX. Excellent ride and handling. The only odd thing is that the tread depth is rather shallow, even when new. I had them on for one week when I had my LR4 in for service. On the dealer inspection sheet they marked the tires as being 25% worn.
I run Nokian winter tires but I wonder if the Premier LTX tread depth will work well in snow. If you live where it snows and are buying one tire for year round, I think the WRG3 is still the best choice.
Hi Paul. First, sorry for bashing so much on the Disco5 you might consider. I'm just personally upset it isn't my dream machine .... yeah, it's this week's 'problem' for overly fortunate 1st world people!
Anyway, about your LTX 19 vs 20 'feel'. I'd expect the 19 to be a softer ride but also less lateral stability - something the lr3/4 doesn't need to be made worse due to it's weight. However, I find my 32" on 18" wheel Michelin M/S-2 to be incredibly stable and smooth and precise. This is probably due to them being E load range and aired up appropriately for the vehicle weight. I use about 5-56 psi depending on set-up that ranges from 7000-8000+ lbs.
Here's something else to really not forget regarding how stable a vehicle feels on certain tires. Regardless of the sidewall, you can still induce a feeling of sway/wallowing/drift by using a tire that is too wide for the wheel. It seems obvious and it also seemed to me like you'd really have to go way past the correct width but I had a direct experience on my BMW. It's factory wheels are 18"x8 with 245/40 tire. I wanted to upsize the diameter just a bit to gain a little ground clearance for snow and gravel roads to trail heads.
It also has the added bonus of 'filling the fender gap' concentrically rather than how people lower the car - which in my opinion, can look silly with a squished top fender edge but still wide gap around the sides. I think my equal gap fill all the way around looks way cooler

This also gains me ride quality sidewall, etc.
So, on to the issue noticed. I first tried a 255/40-18 which pushes the limit on the 'recommended' rim width range while still being inside the range. Went for a drive and the first interstate on ramp curve it just felt like it was going to swish out from underneath me. Very bad feeling. After several back n forth swerves to get a sense of it, confirmed the tires were allowing the body weight to shift too much into the tire.
After switching to a 245/45-18, it entirely went away! These were 2 different tire brands but the shape was also very evident visually with the new one section being flush with the rim lip and contact patch narrower. The 255 was visually wider like you see jeeps running but part of that was due to the design of that tire as much as the proportions of the 255/40 vs 245/45.
Those tires are since worn out and my next winter set is now the Nokian R2 in run flat which is very stable while having the best overall winter/slush grip and still high speed stability.
The Michelin MS2 I use are fantastic at 90 mph curvy roads, etc but the E load range and proper high psi makes a big difference too.