I've not used Snuffers but have used Grizzlies for a few years.A Grizzly type broadhead might make it threw the thin part of the scapular flat with a 550 gr arrow or not.There is also the spine of the scapula and the head.You aren't getting through that.
If you are sure of a gut shot,choose the Snuffer.If you are sure of a shoulder blade shot,choose a single bevel and pray.
Of course,I'm being facetious.You can't possibly know.Here's what I think.You need to do everything in your power to avoid both hits.Here are some thoughts:
1.If you tend to get excited,spend more time pre-season,getting close to deer (out of your hunting area).Get used to being close,letting them pass,going through the motions of making a shot.
2.Tune your bow to the max and get it as silent as you can.
3.Of course,always work on your shooting,especially with hunting situation shots.
4.Don't shoot at alert deer.Pick your shots and don't be afraid to pass if everything is not right.
5.Wait for closer shots if that's what it takes to place it where it needs to be.
Neither broadhead will be your salvation.Both are excellent and have their place.I just don't think they are the answer here.A 45 lb bow can do the job and well, when everything goes right but it doesn't leave a lot of room for error.That's why I believe that shot placement is key and anything you can do to assure that is the way to go.
Good luck with it.