If you are looking for a solid range rifle, you may be looking for an AK74. Below are a few reasons why you might want a good quality AK74:
Cost per round:
5.45@~0.21 per round.
5.56@~0.33 per round.
You would save about $120 per 1000 rounds, which might be a good reason to lean towards an AK74.
The AK74 has a simple design and requires far less maintenance to keep running. This cuts down the time you will spend maintaining your rifle and time you will spend shooting your rifle.
This is a wash between the two rifles. The 5.45 is designed to tumble, and the 5.56 is designed to yaw and fragment. The average shooter would be happy with both rounds, and I would not expect a big difference in accuracy for the average shooter. Practice is key.
The standard AR15 has approximately 4lbs of felt recoil. The standard AK74 has approximately 2.5lbs of felt recoil. I find that the AK74 wins in this category, because although they are fairly close in felt recoil, you do not have the annoying sound of the recoil spring in your ear when shooting the AK74.
Both are pretty impressive rifles, and the AR15 has a lot of upgrade options. With that said, there is just something about the AK74. I own both, multiple configurations and variations of each, but when I go to the range I prefer to shoot the AK74 over the AR15.