I generally haven't needed medical care (except ophthamology and dentistry), so it didn't seem to make much difference whether I signed up for an HMO or a PPO ...
It doesn't make a difference until you need it ... several months ago I came down with a non-life-threatening but very annoying set of symptoms and needed to get a referral from my HMO.
This was delayed for 10 days here, 10 days there, etc., with my condition worsening every day .. Finally I had a provider call me to cancel an appointment because the referral hadn't come in yet. In desperation I finally said "what if I pay cash?" She said, OK, let me get that number for you .. it turned out to be ... $274.
Since one of the incentive for signing up with an HMO is one of cost (HMO free, PPO $100 to $200 per month) ... I chose the free version, but to undo the couple of months' delay built into the HMO system, how much would I have paid? $2000? $3000? It's hard to measure, but easily something like that.
Just a warning to anyone considering this choice ...