I've had a Disco 1, 2 & 3 and the best value for money is a Disco 2.
My D1 suffered so much rust is was untrue, however the D2 was awesome, the TD5 engine never missed a beat and was still going strong when I sold it with 190,000 miles.
Although the D2 didn't have any rust it did have a few fluid leaks (it's a land rover) not from the engine, but the transfer box and axles etc. None of these cost a lot to fix and servicing was cheap too.
The difference between each model is massive it terms of the drive, so I would say look at the D2 and look as many as you can to find the right one. They are easy to drive and parts are cheep
You can even join the D2 boys club forum which I found very helpful