Get a TD5. The Disco 2 looks way better especially if you get a late one (or fit the newer lights to an early one) and they are a much nicer landrover to drive overall and with some tuning, are very capable engines too.
Service parts and maintence are abit more expensive alright of course compared to a Disco 1 or Defender but if you get a good one to start with and replace stuff as they need to be or before problems get worse and service it regularly, it's worth it I think.
If I wanted a 300tdi, I'd get a Defender otherwise a early ropey Discovery if I wanted something to abuse as some of them are so cheap now! Even thought about getting one during the week until I have the gearbox replaced on my 110 as a used Defender TD5 gearbox costs about the same as a rough disco 1 over here
If the air-suspension is working well and you find one with a center diff-lock, the TD5 will be better offroad (with the basics like better tyres and without spending a lot of money on mods) especially with the help of the Traction control. May not have quite as much articulation as the Disco 1/Defenders but if you need that much, you probably should be looking into building a purpose built offroader.