Depends..
OEM's chose how they want to tune their motors, there are many variables to how an OEM chooses. For example, cost, performance, longevity, elevation, fuel, mpg, etc. They basically choose a tune that is ideal for what they think is important out of all of the above conditions, including manufacturing differences.
Basically every vehicle, whether built on the exact same day, at the same place, performs a bit different. Some may have an extra 5-10hp others may have less.
I am a firm believer in "tunes". almost Every vehicle I have owned has had one, and I have had an increase power, driveability & mpg, and contracry to what everyone thinks, they have also been just as reliable as stock. BUT, I have been paying for custom tunes, and I watch what gas I put in my cars.
For example, My GMC 1500HD, was a completely different truck (in a great way) after I got a blackbear custom tune. Not only did I average 1-2 mpg better than stock, the truck didn't feel sluggish like stock. And I had them give me a tow tune, that drastically helped in the mountains, truck would hold rpm whenever I wanted.
Is it the be all and end all. Depends. It costs money, as the custom tune isn't cheap, and I end up putting higher octane gas in. but IMHO, and on the vehicles I have, it was money well spent.
I will be getting a custom tune for my Ecoboost, just waiting til summer.