I have used all of the knives that you described in your post. While they do all work, personally, I prefer a fixed blade knife over a folder. My favorite is the Swiss Mora S1 knife. I was introduced to this knife by Mors Kochanski.
It is small enough to carry anywhere without freaking people out, yet it is an incredibly strong and versatile knife. And I've used mine in Alaska in -40 degree weather and I've had no problem with it. The Mora SI is the best of the Mora line-up. All the others, IMHO, are not worth the $$.
Here's what mine looks like:
http://i238.photobucket.com/albums/f...ra05_jpg-1.jpg
Been using it for about 8 years now. . .LOVE IT!!! :D