Matching the bullet to the velocity is always something to keep in mind. But there are plenty of quality 10mm bullet designed for 10mm velocities. Also 10mm Auto pushing similar weight bullets a lot more than 100 fps faster than 40S&W, more like 200-250 fps faster. With the right bullets that does make a difference.
I'll disagree with you, from the reloading I've done and more to the point, pushing both 10mm and .40 I've found there to only be about a 100 fps difference between them. Case in point, a G20 vs a G22, almost the same barrel length but the 10mm from that 4.6" barrel (I use KKM barrels for the warm stuff) will toss a 180gr JHP to 1350-1375 fps. A G22 will push the same bullet 1250-1275 fps. The G23 vs G29, a 180gr @ nearly 1300 fps vs one at 1225 fps, so I mean yeah, about 100 fps is right. Sometimes a little more, but sometimes less. That's why I have to wonder, having owned quite a few 10mm's, whether it's really going to "do" anything the .40 won't.