Well if you are mounting it someplace on the BC and you can’t see the sheath with a mask on you probably don’t want a pointy one :)
The trouble with knives is they are a two handed operation, one holds the knife and the other holds the line to be cut. I prefer shears, garden shears will work but stainless steel ones from IST, ScubaPro and others will last longer. The cheap EMT shears won’t cut fishing line leader and the pivot pin apparently isn’t stainless and soon fails.