Short answer: Pros: lower in-network costs through a PCP, plus some out-of-network coverage. Cons: referrals are usually required for full coverage, and out-of-network care costs more.
POS plans give you a foot in both worlds. The advantages are lower in-network costs (managed through a primary care physician) combined with the safety net of out-of-network benefits. The disadvantages are the added steps; you generally need referrals for the best coverage, and higher cost-sharing when you go out of network. They suit members who want mostly managed care but occasional flexibility.