Short answer: Pros: lower premiums than a PPO and usually no referrals. Cons: no out-of-network coverage except emergencies, so you must stay in network.
An EPO can be a sweet spot: it usually skips the referral requirement (like a PPO) while keeping premiums down (like an HMO). The main drawback is that there’s no out-of-network coverage outside of emergencies, so an unexpected out-of-network bill falls entirely on the member. EPOs work well for people comfortable staying within a defined network in exchange for lower cost.