i also had difficult 'first AR' decision. my only experience shooting AR was norinco and colt iur both in 556. loved the colt as it was very accurate, but it weighs just short of a school bus...heavy, and pricey.
so i went with the NEA PDW 7.5" in 769!!!
short. light. concealable in 5.11 backpack. lifetime warranty. low recoil. accurate. $0.18 a cartridge to shoot. great customer service. takes beowulf mags for 14 rounds of 769 each mag. reliable. reasonable price. AWESOME!!!!!!