having owned a 200 tdi disco, and currently running a 300 tdi disco, i am much more inclined to say that the 300 is definately more refined/quieter than the 200 was - if that's down to soundproofing then fairy snuff.
my old one had done 220k when i sold it, and my 300 has got 162k on the clock and still returns 40+mpg on a run.
having used it twice so far for towing, once light duty, and yesterday for pulling a 1 ton mini digger and about a ton and a half of dirt on a 16ft ifor williams twin axle trailer (must have been close to the 3.5 ton limit) it definately pulls better than both the 200 and the v8 ever did.
to be fair, everyone is going to have their personal favourite, and there are bound to be a few out there that never have any faults, law of averages states that.
IMHO i would say that the 200 is better suited to the defender than the disco, and likewise, the 300 is better suited to the disco.