Yeah, the DIFFERENCE is efficacy. Efficacy in health insurance is not much different than with vaccines - you have to hit the largest percentage of the population possible to really be effective. When large numbers of people opt-out they are just screwing themselves, they're screwing everyone.
And that's the reason for the mandate, we need to have every single citizen in the pool; how that's best accomplished can be debated, letting people opt-out without relatively severe penalties can't be allowed under any circumstance.
Again, as far as I'm concerned trying to weave this universal fabric over our entirely corrupt, for-profit, million-payers system of insurers / [large] providers is an entirely sub-optimal hack which leaves the system as corrupt as it was beforehand and achieves no benefits of scale.
It's the reason why you can opt-out of public education by sending your kid to private schools, but your still going to be paying for public schools.
Libs are so cute when they show their authoritarian colors.