Is there such a thing as a winner or loser in non-contact practices? The short answer: Yes and no. It depends on the position.
NFL receivers and defensive backs don't wear much padding in regular season games, and there are rules against contact past five yards. The only thing absent might be press coverage, but nearly all of the other traits coaches are looking for in receivers and defensive backs can be measured in organized team activities (OTAs).
On the other hand, defensive and offensive lineman can't hit each other. How are these guys supposed to look good in OTAs? It's nearly impossible.
Then there are neutral positions like linebacker, running back and quarterback. Some things can be measured, but just as many can't be in OTAs.
There are other ways a player can be a loser in OTAs—The player could choose to not participate or be injured and find himself unable to. It's pretty hard to be a winner when you don't even play.
Just the same, there are other ways a player can be a winner in OTAs. Absent or injured players sometimes open the door for a young player to take reps with the first team. Depending on the player and position, getting reps with the first team can be an opportunity to win a key backup job.