D3's have one main disadvantage over a Defender, ramp over angle. A D3/4 from memory has about an extra 100 mm between the wheels comared to a 110.. If you have the same lift and tyre size compared to a 110 then the Disco has a lower limit to what it can crawl over as its way easier to end up sitting on your chassis rails. Especially so on a coiler which usually is limited to a 2" lift.
Defender owners carry on about how most Disco owners aren't up to doing the tough tracks because we are afraid of wrecking our vehicles, but in reality you see very few brand or near new Fenders out there getting bashed around either. The vast majority are reasonably old bits of gear.
Most Defenders out there getting seriously bush bashed are around the D1 or D2 age. So the jibes bout us being pansies afraid of scratching our Disco's is no different to the majority of late model Defender owners. (RVR110 excepted)
My D3 with an e-diff, 32" MUDs, at off road height and with Llams set to max in Rock Crawl will go most places any Defender will go quite easy. Once you have a bull bar plus rock sliders and under body protection fitted you get a much higher level of peace of mind that your not going to destroy it in the rough stuff. Plus we don't have diffs to get hung up on in rocky terrain which is not that uncommon to happen to Defenders if the drivers don't pick their lines well.
Will it go where a highly lifted twin locked Defender on 35" + MUDs and crawler gears can go? No it won't, but put the Defender back on 32" tyres and that would even it up considerably and possibly even give the advantage to the modded Disco. That is a bit of speculation though as not to many Fenders out there on 32's doing the hard stuff to compare against.
D3's are very capable off road and on and are way nicer to drive than a Defender, it just depends on how far you want to go with mods and how much your prepared to scratch / dent your vehicle to find out.

