Honestly, I have never understood where these questions come from but the answer is NO
I am assuming you are talking about legitimate studio rental discs.
There might be more trailers included on a rental disc or some extra content not included but the data content of the main movie is identical.
There might be an exception where a xfer error is made on a rental and then corrected for the retail version but those are exceptions, not the rule.
Remember, that they would have to xfer the movie twice [twice the payment for the studio in terms of encoding] if they did what you suspect.
Also, they would be crippling their disc sales by doing so as a lot of people determine whether to buy a BD based on what the rental looks like.