I have killed quite a few deer with Thunderhead 100 grain fixed blade broadheads. All have been complete passthroughs with the exception of one shot that was a direct spine shot that dropped the deer in its tracks.

Almost all shots through the kill zone only have to pass through the rib cage. This should not be a problem whether fixed or mechanical.

The mechanicals add a significant unknown factor that I don't wish to deal with, and that is the chance of malfunction causing gross innacuracy.

My vote is for fixed blades shot from a paper-tuned bow with the vanes aligned with the blades on the broadhead.