I think it depends the age they both are.
A 15 year difference between a couple that is 25 & 40 is much different then one at the ages of 40 & 55 for example.
I dated a woman who was 7 years older when I was 21, when we were alone or with family there was no difference but when we went out with friends, especially mine because they were younger, the gap was more apparent because of the maturity level.
Once I got into my 30's and as we both got older, friends matured, it really didn't make a difference and the 7 year age gap was a lot less apparent. People actually used to think I was older than her. Not that I looked older then my age ,but because she looked younger than hers... just want to make that clear :smile: