Really, it depends on the situation. I was homeschooled until 10th grade, and from then on I went to a public high school. Like a lot of other things in life, homeschooling is what you make of it.
The inherent flexibility allows motivated people to do very well; in many cases better than they could have in the traditional school system. This is especially true in areas with a low-performing public schools. However, there is little to nothing preventing someone from completely wasting their time and not learning anything.
As far as socialization is concerned; the same "it is what you make it" axiom holds here as well. Co-ops and private tutoring services exist that offer more traditional classroom-style courses in various subjects; particularly ones like science that individual households are unequipped to provide at home. Extracurricular activities are available too; the YMCA, various church, co-op, or community leagues in most popular sports.
Finally, it's worth remembering two points:
Firstly, that parental involvement is the number one predictor of student success and on average homeschooled students have higher levels of parental involvement than others.
Secondly, that merely attending a public school is no guarantee of anything; the public school system produces no shortage of academic failures and social misfits.