neither is important, the sex will be amazing (granted both of you are interested) whatever he's 5 or 10 inches or has a grape or grapefruit for knot. imo it's the knot root (the "tether" behind the knot) that delivers the most pleasure, the pulses of it against your anus/vagina.
and tbh, i don't think genital size is ever important beyond "do we fit?"