A lot of the knives mentioned will do the jobs you asked. Remember the most important knife to buy is the one that is COMFORTABLE in your hand. It can have the best grind, steel, and scale materials, but if it doesnt fit your hand like a glove, you wont want to carry it. With that, there are a few knives that I enjoy and would like to recommend to you. Most have already been recommended, but perhaps I can help re-affirm their recommendations and your opinions.
For 3" plainedge folder, I think it all depends really on what you want to use it for. For daily utility chores (light/medium/heavy cutting) I recommend these top 3 knives:
Native
-CPM440V blade, holds an edge forever!
-comfortable spyderweb pattern FRN handle with dual finger choils, including one on the blade itself for detailed cutting
-deep carry clip, reversible and easily adjusted
-swedge grind for increased stabbing/plunging cuts (self defense if needed)
-hollow blade grind, with thick blade stock for durability
Calypso Jr. Lightweight
-VG-10 steel. Holds a great edge, very stain resistant
-flat ground all the way to the spine for increased slicing over hollow grind
-unique FRN pattern (fish scales) with finger choil
-reversible clip
--there are 2 schools of thought on which is more comfortable between the Native and Calypso Jr. Ltwt. Personally, I think they are both great in my hand and fit well with how I like to hold them. (pushing the bottom of the handle into my palm). Also, they are nice in reverse grip. (I have medium/large hands)
Delica/Standard
-ATS-55 steel
-standard has g-10 scales, which are a giant improvement, IMHO, and can be had cheaply at smokey mountain knife works
http://eknifeworks.com
-comfortable handle
-pocket clip
-hollow grind
As for the spyderedge knife, for daily utility, I dont really advocate the matriarch. I look at that knife more as a self defense/scare the bad dude out of his pants type knife. The harpy comes a little closer for general utility, but personally, I would throw down a nice large serrated Endura or Wegner.
Also, if you want to throw a little self defense into the mix with your plainedge 3" try a Gunting!
hope I could be of service
--defiant
Heading up the SERE support coalition since 2000.
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God made man short and tall.
Samuel Colt made them equal.