Rejoice if you have both!
You get an interesting pair of rifles by sighting one the less expensive 100 gr .243 loads to the same point of impact at 400 -500 yards as you get with one of the premium 180 gr '06 bullets .
Put the same model and power scopes on both and use the .243 for plinking, varmints, antelope, and the smaller class deer. All the shooting lessons, including sight picture and windage, will transfer very nicely to the heavy 30-06 load for those less frequent occasions when the larger cartridge makes better sense.
Other cartridge combinations work too. For more info, there is a discussion at http://shootersnotes.com/articles/paired-rifles/