There are many volatile organic compounds emitted by manure, along with more commonly recognized gasses such as methane, ammonia, etc.  Much of what you smell is the volatile organics, not the ammonia.  Open a jug of household ammonia, and that will 'calibrate' your senses.  At the very low rates that ammonia escapes from manure in an open field, I don't think the human nose can detect it.

As for side-by-side comparisons, the knife/injector itself clouds the picture, because the soil disturbance introduces oxygen, accelerating decomposition of previously stable soil OM and releasing N and other nutrients.  

I don't doubt that injecting manure reduces losses to the atmosphere of ammonia, but at what cost?  The ammonia losses probably aren't as great as you imagine.  The horsepower to pull the shank doesn't come at zero cost, and the tillage releases CO2 and damages the soil.  By placing the manure at depth, you increase the potential for losses by leaching. 

If you are in an urban area and we're talking about liquid hog manure, then I would agree that injection is the only practical route at the present time.  Just try to do it with as little damage to the soil as possible.