In the six years I was an EMT I never needed a knife. Whatever I needed cut I could cut with my EMT shears. As a volunteer FF I have needed a knife just once in 22 years. It doesn't really matter what blade you have. Purchase the best one you can afford to loose on a chaotic scene and not have a heart attack when you do loose it. I do recommend a sheeps foot blade though.
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If it ain't bleeding, it doesn't hurt.