This is a male thing to say the length makes no difference.
I had 165s on my first 2 road bikes. When I bought the bike I have now, shop owner tried to convince me I needed 170s "to unleash my inner power." Yeah, except I am a super spinner, I never stand, and I hate mashing. I generally use the easiest gear I can, that gives me enough power to do what I need to do. While I do ride in the big ring somewhat, it's never more than about 25% of the time, because it hurts my knees the next day.
The minute I hopped on the bike after it was built up, I felt the difference. Every pedal rotation was a strain and I felt like I was pushing like the bike did not fit me (it did, other than this).
I had to beg and convince the guy to order me the 165s. He knows better now. I am a short, endurance type rider in her late fifties, not a racer. I need to be comfortable.