The Conti Twinduro vs Michelin t63 debate again... I can report that the Conti's are an excellent tyre choice, I've worn several pairs out (rears last ~ 2500 miles) with a mixture off offroad, road and competitive trials. On road, in wet or dry, you can corner extremely hard and abuse the brakes to no ill effect... off road, with a security bolt run at ~15psi and they are good other than in deep mud. Being mainly an offroader, I've changed to an 18" rear wheel & run a Pirelli trials tyre - whilst it's better, I still got up most things with the Conti... it was that good.
I have found a better rear though, if you have an 18" rim, an IRC - a bit more aggressive than the Conti but still good on the road, which I'm running with a Conti front.