I personally don't like the Swhacker concept simply because you don't get full expansion until entry. Now granted, using a high speed xbox and a heavy bolt you will almost always get a pass through. However, should you happen to punch the near shoulder joint (which I believe you would bust) and then somehow manage to hit the opposite shoulder joint or leg bone, you may not get a pass through and you're left with only a tiny hole to leave a blood trail.
I would prefer, if using a mechanical, to use something like a Rage or G5 that opens on impact leaving a big entrance hole. Even if you don't get a pass through.
You can argue the effectiveness of the Swhacker all you want. I just don't care for them and will likely never use one. And as far as quick kills, I've used Magnus Stingers for years and had several deer drop within sight going less than 50 yards. Including a huge legitimate 200+ lb. 10 point.