Navy, congratulations on never making a margnal hit. You asked a lot of questions with a lot " depends" type answers.
Don' t you lose 50% of your cutting ability with a two blade over a three blade?
This depends on what you are calling cutting ability. Do you mean the actual cutting surfaces. I sometimes use a two-bladed stos head that actually has more cutting surface then a lot of three bladed heads. Or do you mean penetration cutting ability (cutting as deeply as possible). A lot of two bladed heads may actually penetrate a bit better on game.
On a marginal hit the extra blade may slice an artery.
True, it might. On the other hand on a marginal hit, you may only have enough penetration to puncture one lung, where as you may be able to get two with the two bladed head. It' s a toss up of what you need in the head, and what game you are hunting.
A two blade with 1 1/8" diameter is bigger than a three blade with a 1 1/8" diameter. Right
Bigger? I don' t know what you mean. I think it would be the same diameter.