Either/Both would be a great choice.
The .25-06 with 100gr MK is a great varmint round, and the 100gr TTSX is a darn fine big-game bullet. The two are usually interchangeable as far as POI goes, IME.
The .243 with 105gr AMAX is a great LR varmint/deer bullet, and the 85gr TSX and 80gr TTSX are excellent on deer.
If you plan on shooting a lot of small varmints then the .243 is awesome. If you want to shoot some coyotes and deer, then I'd probably get the .25-06, but you really can't go wrong! Just remember that it's ALL about the bullet, and minimally about the cartridge that the bullet is launched from. You have the 105gr AMAX and VLD, and the 85gr TSX in .243, and the 115gr VLD and 100gr MK and TTSX in .257.