I've used both 606 front and 908 rear combos on my 990 and 950 SE, aswell as 606 front and Tractionator Rear combo on my 950 SE. I think the 908 will give you better wear on road, and will provide all you need off road, but the Tractionaotor will give you much better grip in the dirt, rocks and mud. My rear Tractionator was 70-80% worn after a 12-15 hr. off road rally and a 3 hr. road burn. But I was loaded with fuel, bags and moving at spds. of 130 -140 kph.on the tar. The 908 will last you longer than that, butnot as much aggressive grip.
That all being said, I have a brand new Tractionator waiting to go on my SE again. They are much less $$ than the 908, and I'll try it again with limited ashpalt use.
Hope that helps...
I think you'll be fine with either, as long as you keep spds down on the tar.