For any real offroad riding (other than hard packed trails) lighter is better. My last offroad course we had our choice of KTMs from the new Freeride 250 to the 350s and 400s and 540. For my preference (inexperienced) I preferred the Freeride (light and easy and low) or the 350s (light, easy but high seat height). The 400s and higher were very difficult to modulate the gas, therefore frequently had the slip the clutch (which is apparently par for the course offroad?).
For onroad riding once you've had the POWER it's hard to look back. I had a GS 1150, which was a great tourer, but too heavy and not very exciting in the engine department..you really 'ride the waves of torque'. The GS1200 is just too 'plasticky' for me and there are simply too many on the road.
Now I have the Triumph 1050 and love it. Powerful engine, but you don't feel like you HAVE to go fast. Any complaints are relatively easily and cheaply fixed (progressive springs, add lights, adj clutch/brake levers, etc.). It's a bike you can work on and improve a little at a time.
For the psychology of adventure bikes and a good review of the Explorer see below, which I thought was a very well written article:
In the end you have to correctly choose what you like to actually do with your bike. Do you actually ride off road, or just like the thought that you could?
The spectrum runs from KTM (990/950 ; better off road) to BMW GS (best compromise?) to Triumph Tiger (better on road). I haven't ridden the Explorer, but from the review it stills seems to be suited more to the road.