It depends how much deductible you need to pay before all medical claims are fully covered by your insurance company. If your dedictibles are low, then PPO is definitely better than HMO. With PPO, you get to choose physicians at your desire and in case of medical emergency like going into a surgery, the approval process is much easier and faster than HMO.
I just had a baby 4 months ago and i was insured by PPO, it really did not cost me too much money. $1000-1500 for entire pregnancy.
I hope it helps =)