Not only do deer have stronger noses, but they also have more brain matter dedicated to analyzing scent. They can detect faint odors and not get washed out by stronger smells. Deer will still smell you with any scent cover, but some of them will risk human stink for delicious vanilla stink.
Most scent blockers are antimicrobial sprays. This will reduce the odor coming off of your clothes as they get dirty. This could also be achieved by wearing clean clothes and preventing sweat. Deer will still be able to smell you, but it could possibly be enough to get them within range, but probably not.
I used to use scent blocker, and don't anymore. I get winded just as easily as I used to. I've also had deer come right up my scent trail after living in my truck for a few days, I was ripe. Some deer don't respond to scent normally. Just like how some people see a city block being burned down as a peaceful protest.
Hunt the wind and choose your way in carefully. In my experience, deer will bed in view or down wind of common entry points. These products may give you a slight advantage, but skill cannot be purchased.
