ACA/Obamacare is major medical coverage that can not be denied due to pre-existing conditions. It is very affordable if you get a large government subsidy on the monthly premiums.
Private insurance is usually the best option if you don't get a subsidy and especially if you are healthy. These plans are generally better coverage and cheaper premiums.
Employer plans are GREAT for the employee but once you add a family member/members the premium can get outrageous. As a health advisor I do check the private market to see if it would be more beneficial to put the other family member/members on a private plan.