Minimum bullet weight for elk in Colorado is 85 grains not 143welcome to the forums!
Colorado requires your bullet be at least 143 gr with a centerfire rifle for large game.
I like both rounds but for elk I would prefer 308…. 30 cal is a killer. The 308 will also carry more energy at 500 yards and it is suggested you should have 1500 lbs of energy to kill an elk.
Frankly, either rifle will work with a double lung shot…. Make sure you are in great shape and good hunting!