Too bad the search function is broken. I would refer you to earlier diatribes I've written on this popular topic.
I avoid partially serrated blades. I would rather carry two separate knives, one serrated and one plain, than sacrifice half of a perfectly good plain edge. Serrations are great for some kinds of cutting, but when you don't want them they can be a real pain. Since I can almost always carry multiple knives on my person, having one blade that thinks it can do it all really isn't an issue. If for some reason I could carry just one knife, I would choose plain edge. But that's just me.
Manufacturers and dealers tell us that combo-edge variants outsell all others of a given model by a wide margin. I think the majority of customers simply don't know what they want, so they opt for a little of both. Having said that, I will admit that there are some knowledgeable individuals for whom a combo-edge seems like a reasonable compromise. Are you one of the latter? It's okay if you are; you've got lots of company.
I think people buy combo-edges for one or more of the following reasons:
a) They can't make up their mind, and buying/carrying two knives is not an option.
b) The dealer tells them combo-edges are the most popular choice.
c) They think the combo-edge looks cool.
d) They can't find the model they want in a full plain or full serrated version.
Incidentally, I do not mean to imply that the above reasons are not valid, or that people who opt for a combo-edge are crazy, stupid, or evil.
By the way, have you read Joe Talmadge's informative FAQ on the subject of plain vs. serrated edges? You can find it here:
http://bladeforums.com/features/faqser-plain.html
I hope this helps.
David Rock
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Stop when you get to bone.