I think it's less about what formal powers the different branches of government have, and more about how they use them in practice. As a parent comment said, the USSR constitution was good on paper, but not so much in practice. On the other hand, here in the UK, the queen technically has supreme power over everything (and even ignoring that, our Prime Minister is head of both the executive and the legislature), and yet in practice this doesn't get abused too much (arguably recently that has changed a little).