I think everything's been pretty well covered here already. Financially it's not the best move of course - Jeeps have outstanding resale while Rovers...not so much. And the Rover will have a higher maintenance cost as well. Further, for the really technical stuff a Rubicon is simply going to go more places than an LR4. And when it comes to aftermarket there's simply no comparison, either in availability or price.
But on the positive, the LR is a much more civilized platform on the highway. It has far more cargo capacity, far more towing capacity, and is just flat out more comfortable and refined to drive. Even without the (somewhat rare) HD pkg rear locker, it's surprisingly capable and will give the Jeep a run for it's money in most situations. Heck, I'd even say it's better in slick stuff when the computers are at their best, like snow/ice covered roads.
Before you commit you'll of course want to spend some time behind the wheel which it sounds like you've got covered. It also sounds like you've done some research into Rover ownership and all that can entail, though to be honest it's not anything like it was with the earlier trucks - the LR3/4 platform has generally been pretty sound. But I would also recommend you look into the options available for building the truck out the way you want it. If you're coming from the Jeep world you may be shocked at the limited aftermarket for these things. Want a front bumper for your LR4? OK, you can chose from ARB and .... uh, that's about it in the US. Rear bumper with tire carrier? How are your welding skills? Because Kaymar was the only option and they've pulled out of the US. (there are more options for the LR3 than the LR4, and I know some companies are looking to adapt their LR3 products to the 4 since they are nearly the same) Compared to the Jeep world, it's enough to make a Rover owner cry in his beer!
BTW, I started out looking for a Jeep. I ended up with an LR3. I still like Jeeps, but I don't see myself buying one any time soon.
My truck is an '07 LR3 with all the OEM bells and whistles. I think I have literally every factory option except rear seat video screens....HSE, HD, LUX, etc. Mod-wise, I'm running an ARB front bumper, a home-built rear with jerry can and tire mounts, Tactical Rovers skids and sliders, Johnson Rods, 275/65-18 Duratracs, and a low profile Urban Offroad rack with a home-made axe and shovel mount. I've got about 115K on it now and knock on wood, it's been quite reliable. I did have to replace my compressor, but I could see it coming and probably could have gotten away with just doing a rebuild if I'd planed it right. It will never be a rock crawler, but I do plan to run the Rubicon in it possibly this coming year.