A 100 gr 243 bullet and a 130 gr 270 bullet have the same sectional density and nearly the same velocity.

I doubt you'd be able to tell very much difference at all in terms of performance on deer sized game inside of 250 yds with identical bullet type in both callibers.

I personally believe that all high power rifles, from 243 to 300 Win perform about the same on deer under most conditions. Some make a little larger hole, but really don't kill any faster. Shot placement is by far most important on deer.