That's an odd mix of choices. I can't comment on the Daihatsu other than to say if they were brilliant more people would own them. Then again, the Nissan Patrol isn't all that popular but is an excellent offroader, so what do I know?
I had a 300 Tdi Discovery so can impart my experience there.
4k puts you in MK1 200Tdi territory, or touching early 300Tdi (stay away, there are timing issues until late P/R plate and the damage can permanently affect the engine unless it is repaired early enough or complete failure was experienced). Bear in mind your stopping distance is atrocious (drum brakes on the rear, but unladen weight is 2.5 metric tonnes) and the outer rear-door handle is a dust magnet and prone to seizing. Panel fit is laughable (impacting bodywork repairs) and overall finish is, at best, of sixties quality. These are hand-finished vehicles and no two are alike (look at the rear bumper on two side-by-side). The transfer box on domestic-use only vehicles will also have seized & require attention. Simmonites, among others, do facia upgrade kits so a 200 can be made to look like a 300 for very little money. I had an R plate 300 from new, & I both loved and hated it. No end of niggling faults, but the only really significant one was the EGR valve failure which killed my fuel economy & had me trailing smoke. Expensive to maintain unless you're a DIY mechanic, and if you don't get a mechanical timing belt fitted you're looking at a new one every 48k. The mechanical belt + fitting costs the same as a main dealer 48k service. Bear in mind also that it's a 6 month/6k miles service interval. One alternative is that if you can afford the fuel bill, the V8 is a stormer. Take a look at the landrover enthusast websites for a better picture of both the community spirit surrounding the owners, and of course you'll be able to read all the horror stories.
On the Jeep Wrangler front, this is the closest anyone can get to a 90 without having a 90. My colleague owns one as a weekender. Many argue that the 90 is better, & if you compare the diesels of both that would be true, but the petrol version paints a slightly different figure, and it's an absolute hoot when you give it gas. What is more attractive about the 90 is that it's a classless & timeless go-anywhere vehicle. What's not so attractive is that unmodified it won't go above 85, handles like a breezeblock at anything over 60 and is uncomfortable over long distances.
4K would also get you a v.high mileage freelander, but STAY AWAY FROM THE PETROL ONE!!!! We've got a 1.8 anniversary model, very pretty & my wife won't part with it, but the rover k-16 has a notable design flaw in the head-gasket that LR won't fix for free outside of normal warranty if the engine is anything other than vanilla (ours isn't), and will break between 40-60k miles (ours did). Ignore the offroad purists, this is a decent offroader compared to the same-class lifestyle offroaders & is a comfortable cruiser. Loadspace is disappointing, though. The only thing in it's class that comes close all-round is the nissan x-trail, which is still too new so out of budget.
The trooper is also an excellent workhorse vehicle, & generally more reliable than its competitor, the Discovery. It's not a good road-car though, the disco is marginally better handling though slower. The engine in the trooper has better towing power too. The only thing it doesn't have is the clubby ownership support of the LRs. I nearly bought one to replace my Disco after losing count of how many times I went back to the dealer over niggling faults that shouldn't exist on a £22k vehicle (in 1997).
You may even be within budget for a 3-door 3 litre nissan patrol (the newer shape, not the tonka), but the fuel economy is atrocious and if you tip it over the whole roof collapses unless you fit a rollcage. Also handles like a boat. Well equipped and a great offroader, though.
What am I in now? an 04 plate Discovery TD5 Commercial. No problems. None. If I could have a second 'play in the mud' toy, I'd have a 101.
Sorry for such a long post, & I know many will disagree with my opinions but I hope this helps - you can't have too much information & 4k is a lot of money to make an uninformed mistake with.