I like the Mefo SE rear & a Heidenau K60 front...
the D606 fronts are great if you are going for a weekend ride and want ultimate traction; as mentioned above when they begin to wear things get scary going in to turns on pavement & in the wet. They can be had for about $60 with some looking
The TKC80 front is pretty good offroad, great in gravel so-so on pavement. I ended up with it on my lighter KLR650 where it doesn't have as much work to do and wears well
The Mefo fronts wear funny & aren't as predictable offroad as you'd think
The Heidy K60 works really well on the street (best dualsport tire I've found as I tend to ride the front hard) and doesn't fill up with mud as fast as the Mefo or Scorpion fronts, which just suck in wet/loamy offroad conditions. I've had to turn around in some places when the Scorpions lose the front every 100 feet. Scotts steering damper or not, they are as slick as a bowling ball.
The Mefo rear wears like iron & when it steps out under hard throttle holds it line instead of sliding out. I roasted the last rear doing some insane burnouts, when it was all done it had hardly affected the carcass & there was still tread left. Other tires that have gotten the same treatment have shown cords within a minute of LC8 abuse. Tough tire, reminds me of old-school Metzelers (hmm, ya think?)
950 Adv 'S'
'87 KLR650 - <200K miles
"Like the Energizer Bunny, just keeps going & going..."