As I have said 3 times 100 ft-lbs accelerates the car equally at 3000 rpm as it does at 6000 rpmgeneral hough the HP is double. Doing more work, is not accelerating the car at a higher rate. Think of it as working smarter not harder.
What you are leaving out is gearing the 6000 rpm engine needed deeper gears to get the best quarter mile time over the 3000 rpm engine, say for eg. 6000 rpm engine needs 4:1 and the 3000 rpm needs 3:1 the 6000 engine will be putting 400 lb ft to the tires and the 3000 engine will be putting 300 lb ft to the ground. And if you ran them both with 3:1 the 6000 engine would just trade acceleration for top end speed with its more HP and RPM capabilities.