A male here looking for honest answers. A few years ago I lost a lot of sensation in my penis so sex is now more about mental stimulation than physical. Needless to say, I am usually not fully hard during sex. I asked my last girlfriend about it and she said it doesn't really feel any different, except for I'm less "pokey" (I'm pretty long). I'm hard enough to penetrate, but not by much.
I am not sure I believe that because any time I get fully hard during sex, the girls react immediatly. More noises/squirming etc.