Perhaps I should metion, I'm not talking about ALL mechanicals or ALL fixed heads, but proven successful ones with stellar penetration and flight characteristics (such as Muzzy, Steelforce, Steelheads and Snypers to name a few).

I've killed a deer in the past with a large diameter cut Wasp Jackhammer with a less than desired KE bow set up, but did not get a pass through, so I wouldn't use them again, even though I'm now shooting a high performance bow. But we see glowing penetration reports of both Muzzy and Steelheads so often, I guess where I'm going with this is if flight and penetration qualities are equal, but you must choose only one, which would it be, fixed or mechanical?