having driven both the P3D- and XP90DL, I can kinda see what the OP is talking about.
The 3 is lower (duh) and feels planted to the ground. acceleration is forceful and consistent. i didn't feel much decrease in the 80+% range. during acceleration, everything is solid, the car moves in one whole piece (if that makes sense). on a flat smooth road, all you hear is the whine of the motor.
The X, even at the lowest setting, definitely feels like it hauls itself and all it's moving bits with it throughout the powerband. i always having it in ludicrous mode (because, why not?), i dont know if its because it's just a bigger vehicle, but when i punch it, i can hear the squeaks of the doors, seats, and everything else with a movable joint. it doesn't feel that much faster because of all that
until i put it in "max battery power". after supercharging, I treat myself on the way home by doing this, and let me tell you....that "lightspeed" graphic on the screen is seriously what it feels like. it's so damn fast all those rickety parts don't have time to shake around and the whole thing just hauls ass. it reminds me of the 3 (just way faster of course). either way, I was happy to have unlimited supercharging because I burned through range like nothing else.
so, yea....butt dyno wise, it
feels closer, and to some that's all that matters (the experience), but if you were to compare them side by side during acceleration, you can see how different they end up.
I completely forgot about my dragy. it's just sitting around with the rest of the stuff i cleared from the 3 when I sold it. will need to capture some runs on the X