Well they are both based on a necked down 308 hull. The 243 will shoot a little flatter (not much flatter however) but only because the heaviest bullet weight for it will be 100 grs compared to about a 140 gr bullet for the 7mm-08. But the 7mm-08 is by far the more powerful and deadly whitetail gun and will kill black bear and even elk with the right bullet. And it does this without knocking your shoulder out of joint. In fact with a good recoil pad its really not much worse than a 243. Remington also makes a 120 gr hollow point in 7mm08 that will make a 7mm08 a very flat shooter and is perfect for coyotes and other varmits. Heres a comparison chart. The top line in each category is a 100 gr 243, the second a 120 gr 7mm08 and the third a 140 gr 7mm08.

PRINTER FRIENDLY

Index No. Cartridge Type Wt. (grs) Bullet Style Primer No. Ballistic Coefficient
243 Remington Express 100 Pointed Soft Point Core-Lokt® 9 1/2 0.356
7M08 Remington Express 120 Hollow Point 9 1/2 0.343
7M08 Remington Express 140 Pointed Soft Point Core-Lokt® 9 1/2 0.39

VELOCITY (ft/sec)
Cartridge Type Bullet Muzzle 100 200 300 400 500
Remington Express 100 PSP CL 2960 2697 2449 2215 1993 1786
Remington Express 120 HP 3000 2725 2467 2223 1992 1778
Remington ExpressC 140 PSP 2860 2625 2402 2189 1988 1798

ENERGY (ft-lbs)
Cartridge Type Bullet Muzzle 100 200 300 400 500
Remington Express 100 PSP CL 1945 1615 1332 1089 882 708
Remington Express 120 HP 2398 1979 1621 1316 1058 842
Remington Express 140 PSP CL 2542 2142 1793 1490 1228 1005

SHORT-RANGE¹ TRAJECTORY*
Cartridge Type Bullet 50 100 150 200 250 300
Remington Express 100 PSP CL 0.1 0.7 zero -2 - 5.4 -10.4
Remington Express 120 HP 0.1 0.6 zero-1.9-5.3 -10.2
Remington Express 140 PSP CL 0.2 0.7 zero -2.1 -5.7 -11

LONG-RANGE² TRAJECTORY*
Cartridge Type Bullet 100 150 200 250 300 400 500
Remington Express 100 PSP CL 1.6 1.5 zero -2.9 -7.5 -22.1 -45.4
Remington Express 120 HP 1.6 1.4 zero -2.9 -7.3 -21.7 -44.9
Remington Express 140 PSP CL 1.8 1.6 zero -3.1 -7.8 -22.9 -46.8