This one's interesting. Straight cis-female here; have oral-ed and been oral-ed on by both genders in my younger days.
From a sensations standpoint, my experience (which I'm sure isn't representative of the wider pop) is that a girl going down on me feels akin to a cat lapping milk, while a guy doing it feels like a dog lapping water. Force and suction can get more powerful with a man, but it's psychologically more mind-bending when a girl does it. It's all pleasure at the end of the day.
I'm curious if there is a difference, for any gay vs straight men, when a guy vs a girl does it for them?