if I were GOING to a knife fight!... A Scottsmans Sgian Dubh Double Edged Dagger - about 10" blade and a good Hand and a Half Claymore Sword - 45"!
For self defense... the Spyderco SOCOM folding tactical - straight edged hard blade
When jumping out of perfectly good airplanes with only some string and a sheet.... a kershaw para-auto - serated hard blade
tool box... buck - straight soft edge
Soft blades can be sharpened on a rock anywhere, but loose their edge quick. Hard blades usually require a diamond stone to put a good edge on them and stay sharp a long time.