If I had a 25-06 barreled action (it's a long action), I wouldn't even consider a .243. I'd go with a 6mm Remington in a 1:8 twist barrel. Or better yet a 6mm Ackley. That way you get a better round with the ability to handle long high B/C bullets without sinking the bullet deep into the shoulder. Might also want to consider the .257 Ackley, as it a near perfect all around gun for large deer and smaller game.
I agree with an above post, 6mm remington over the .243 especially if he wants minimum fuss and brass/dies that are easy to get. Just about anyone still makes dies for 6mm rem. and it's got the power of a 243 AI.
Suggest he go with a 7 1/2 or 8 twist to utilize the 115 grn bullets. Both my 243AI and 6mm AI have 7.5 twists and David Tubb suggests using a 7.5 for his 115 D-Tac bullets.
Keep in mind that a barrel chambered in 6mm Remington will still be shooting good when the .243 or a .243AI will be laying in the junk pile. The neck and shoulder design is the reason why. The long neck will make seating long bullets much easier. If I were doing an improved 6mm round I think I'd have to give the old 6mm Rockchucker the nod. It's very similar to a 6mm Ackley, but uses a 30 degree shoulder instead of a 40 degree shoulder. You'll have less trouble with the dreaded doughnut. Also set the chamber up for a .266" neck diameter, and shave the necks to .264". You'll never regret the move.
I've been saying it for years that Savage needs to do the 6mm Remington. It will work well in the short action due to the slight added length of the reciever. Still if your going to use the rifle for deer as well as varmits, I'd seriously have to consider the .257 Ackley