unfortunately you won't find a plan that offers you an in-network panel you can access nationwide. unlike an hmo a ppo will give you access to out-of-network providers but you'll pay more to see doctors who don't participate with your plan. since you can't buy a health plan with a nationwide provider network in any case perhaps you want to consider sticking with an hmo to save money. however if it's important for you to have access to any doctor the ppo would be the better choice. it all comes down to your personal priorities.
i currently have mediblue hmo. i want to have out-of-network benefits so i'm considering a ppo with blue cross. . the ppo plan seems to cost more and give me less benefits. and i am not sure if the ppo will provide me with nationwide (in-network) coverage which is what i need.