Done properly, with dedicated parental involvement and using resources of other parents or outside classes in areas of expertise it is much better. Also plenty of socialization activities, such a sports, arts like music and theatre etc, it can be much better than a traditional school.The opportunities to expand on a subject are endless when homeschooling. The amount of time taken up in a traditional school setting by logistics, and keeping the same schedule of learning for everyone can hold a child back when they need to move forward, or push a child forward when they need more time to focus on a particular subject.
I personally know of two physicians, a dr in theology teaching at an Ivey league school, and many others with advanced degrees and doing well for themselves, that were properly homeschooled.
The flip side is when a parent isn't involved, or doesn't take education seriously. I know of two JWs who were homeschooled, now in their 30's. Both struggle, one still lives at home, the other is supported by his wife!