I feel the 390 is better for me in mud and slick and uphills, at least for now - as the tons of smooth torque there make it easy. You definitely need good technique to ride the little chipmunk in some conditions. Not a beginner friendly bike, but then the heavy and tall 390 isn't either.
I am not having an issue lifting the chipmunk over logs and such, or ruts and up-hills. ONCE adjusted properly though. It can be a hassle if not adjusted... if you screw up the jetting, it will bog down and not accelerate and act weirdly.
You definitely have to try and carry more speed with the small two stroke, as the power is not always there. Much like a kart, flowing with more speed into turns is something you get used to and appreciate.
Remember: you don't get power from the throttle, but the clutch, lovingly known as the "power giver". Heh. Seriously though - work the clutch a bit and you'll have as much power as you want whenever you want, but it takes some getting used to.
On the four stroke, you can whack the throttle all the time: the engine response keeps lots of traction on the rear wheel - not so with the chipmunk: whack the throttle open anywhere above idle and it revs so fast that it chews the rear tire instantly.
Also, no engine braking. It is different - not in a bad way though: the little chipmunk works in "power pulse" mode where you can roll off the throttle and coast then roll on an impulse and roll off and coast etc. With the big Berg, every roll off the power is like putting the brakes on, so often you coast through turns with the clutch pulled in and the engine revved up looking for that instant power at the exit. Not so with the chipmunk.
This also makes it less sensitive to the throttle: the big bike has either engine braking or torque on either side of the current throttle position - you learn quickly to have a steady hand. With the little bike though, you don't need to be as precise. You don't have to pull in the clutch every time you roll off...
The light bike responds better to rear brake - needed also because of the missing engine braking. I find I need much less front brakes now and it is overall a smoother ride, since both acceleration and brakes are smoother.
I am trying a new technique, of using the rear brakes without pulling in the clutch - it takes a lot of attention right now not to stall the engine, but that actually is the point of it: not to lock up the rear wheel.
I am still working to get used to the abrupt power and often sit down to get my hands to relax from having to hang-on to the bars. Do not think for one second that the little bike is gutless... you have to rev it sure, but it's all there :)
The 390 was/is a lot of fun. I don't feel like letting it go, yet. But the little chipmunk is more fun! It is so light and maneuverable that you literally feel like you're bouncing off the walls with it. The inertia of the extra 40 lbs of the big bore is something you notice anytime, all the time.
Since it is easier to correct mistakes on the light bike, I think it's safer. It definetly makes you a better rider, as you are more aware of what's coming up ahead, what gear to carry through etc.
I have been riding the 150 exclusively for a few weeks now. No way will I bring the 390 to a hare-scramble again. I may take it to a long road-ride. I may sell it next year too.
Read the entire article: KTM 150 XC vs Husaberg FE 390.