It all depends on your motivation for going solar. If you want to maximize long-term savings and increase the value of your home, then purchasing your solar system is best. However, if you just want a low-maintenance way to reduce monthly energy costs and practice environmental stewardship, then a solar lease might be a better option.
Also, note that leasing can be a good option for those who might plan on selling their home in the short term. Leasing panels does not make you eligible for the solar tax credit.