It may have to do with the sequencing of the program. In the first one, you're directly placing the lower() method into the for loop, while the second one is assigning it to the variable, then placing the variable into the for loop.

I tested the second method, and it seems to be case sensitive as well. Perhaps the case sensitivity issue lies in the content of the for loop, and how it works when used with option 1 or option 2.

What did you put into your for loop? I assume you had the same loop for both option 1 & 2, but perhaps there might be a 'clue' in the loop itself?