I would think that you'd get about the same performance with a 95 gr BST in 243 as you would a 130 gr BST in 270.

The 100 gr 243 and 130 gr 270 have the same sectional density, and nearly identical velocity. With identical bullet design, they should do about the same to a deer.

Addressing the 5 grain difference when moving down to 95 gr BST: Since ballistic tips are so explosive, and a 270 has a larger diameter, it should open up to a larger diameter than the 243. Therefore, an expanded 130 gr 270 would have less sectional density than an expanded 100 gr 243. Because of this, I'd think that expanded 95s and 130s would have about the same sectional density.

All in all, you shouldn't notice a difference between the two on whitetail. Good luck...you should have a very dead deer.