Does the HSA work with the PPO? I'd doubt it. Paying an extra $140 ($360 premium-$500 deductible) to get $750 is a no brainer.

Plus, the HSA can be treated as a tax-free retirement account as it is funded with pre-tax money, and grows tax free like a 401k. It can be used as an emergency fund, if you just pay the bills, and not submit them until such time as you need the money, even years down the line. There is something to be said for maxing that out at the $7300 per year, which only reduces your paycheck like $5000 per year.

In light of the c-section, where 20% of $50k is $10k, so you'll hit the out of pocket max on either. The lower max, means the high deductible plan is going to be $1340 cheaper.

I'm having a hard time finding a scenario where the PPO is the better way to go.

I'm on the ACA now, my premiums are going to be $1480/month for 5 with $7500/$15000. To me, your plan looks really good, very generous. Your employer would seem to be contributing 80% or more of your premium. The high deductible plan in that case would be that much cheaper for them, making the $750 HSA contribution for them worth while to push you toward the high deductible.