Our guy friend is probably 8+, I'm 6+
My wife has never said anything about his bigger size, never anything about if he's better, she just says it's different.
It's very very obvious she likes sex with him. There's plenty of hard fast fucking but sometimes she just lays back with her eyes closed and moans while he pumps her slow.
Until we got into this she never had an orgasm from sex, vibrator, oral no prob. We'd been with him quite a few times, one night she was really turned on (like usual), we'd each done her once, they were into their 2nd round. He was on top really going at it, she got quiet, her body got stiff, and she came HARD, that instantly got him off. I climbed on after and she held me tight while we kissed and pumped.
Since that night she cums with him for sure. There's been nights she cums while I do her but only after she got off with him first.
She's super turned on for me after they finish. It's fun.