Red clay is cheaper. Har-Tru is easier to maintain, but it's still a major pain in the you-know-what. You have to have sprinklers, sweepers, line brushes, and rollers.
I grew up having to help maintain my dad's Har-Tru court that he built on his property. I hated it. I think that if you work for a living, it's not worth your time to do it. I will never build a clay court for myself unless I had enough money to pay other people to maintain it.