While i don't have a ton of trigger time behind a 394/395. i have ran them. I like my 066's. They weigh less, like 2-3 pounds. Makes a difference if you are actually using them in the woods, vs play racing. The 395 has better antivibe and better air filtration.... The 066 seems much more torquey than the husky. Kinda like a 046 to 372 comparison if you have ran either of those.
I have two 066's. Both are magnums. I was not aware they made an 066 that was not a magnum, but I am new to the stihls. My old red light 066 has the aluminum flywheel. It is a strong runner. I run 3/8"-8 with 20" on the newer 066 and a 24" with the same rim on the Red light. I had a 3/8-8T rim on the older one with a 28" bar and you still can't believe the torque these things have. You'll wear yourself out trying to make one of these monster bog, in reasonable wood. -under 36". The newer 066 ran with a 36" bar not to long ago with a 7T rim and still had enough ass to pull full comp chain and not bog. That one is stock, with the dual port muffler cover, mind you.
The newer 066's are idenical to the 660's. My other 066 is an 03 model, but is still a 066, although Andy tells me they are part for part idenical. They use poly (plastic) flywheels. They rev faster, but IMO don't carry the torque in the cut. They also have a tiny exhaust port opening on the muffler and only have the single port muffler. The older 066's had the dual port cover. also the newer 066/660's have gay epa carbs, limited adjustment.
My woods modded 066 (red light) totally blows the newer 066 away.
One of these days I may get a 395 to play with, but for now, the 066's are KING. lol. If you are seriously interested, I can call my husky guy tomorow. He deals in a ton of 394/395 saws for the loggers. The last time he had a bunch in, he wanted 300ish out of them, and they were in decent shape. At that price, they don't last too long.
-Steve