The difference between writing the return value of a program with or without "return" is, that using return immediately exits the program. So when the return statement is just the last line in your program I won't expect any differences in behaviour whether "return" is explicitly used or just the value/variable you want to return. I could imagine that using "return" might very slightly slow down execution, but we can't say this for sure as we don't know how its implemented and as its used just once for each program run its sure hard to notice a difference in execution time.
Its sometimes said that using "return" is good programming habit, but ...
The screenshot may indicate that using "return" costs a very tiny bit of time, but I won't bother..

EDIT: Here is a second run which seconds what you had written about it being hard to decide if "return" really slows down the program execution
