Cheapo -
I am no expert on knives, however I just returned from a knifed combatives class, where I found out just how much I did not understand about the differences in knife blade design. The class discussed very quickly the different blade designs, and how they play in the various techniques.
I came away with two major things, besides the training. One I now prefer a fixed blade over a folder for defensive carry on a regular basis. Two I prefer a dual grind over the chisel grind.
If you don't already read Tactical Knives, it is also a good source of information in this area.
You should checkout TFL's sister site,
www.bladeforums.com in addition to this post, they probably have a thread on fixed vs folder that answers most of your questions.
Sorry I could not help more, but I am by no means an expert.
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