The verdict
For a small B2B team with a website that gets steady traffic and an email or CRM tool already in place, I'd pick OptinMonster. Targeting rules, exit intent and A/B testing are the reason to buy it, and it works with WordPress, Squarespace, Wix or any HTML site.
If you run a small online store and want list growth plus email and SMS flows without a second tool, I'd pick Privy. A new subscriber lands in a segment and a welcome flow picks them up, with no export.
If you have a deep email setup and only need pop-ups, OptinMonster is the more focused tool. Privy also sells a displays-only plan for that case, so compare both. Neither has a free plan, so test with real traffic using the money-back window or the trial.