Probably most thoughtful persons would agree Trump isn't fit for President. Unfortunately, it's not obvious (so some of us) that Clinton would be any better.
If Trump is elected, I think we'll have various diplomatic gaffes, and an unusually high number of clashes between the Executive and the other branches. But I think professional advisers will help him avoid major catastrophes.
If Hillary is elected, I think we'll face continued slow increases in income inequality, and in corporate control over government. If there's truth to her reputed role in destabilizing Syria, we might also find ourselves in more wars than we would have with Trump.
Both candidates are unlikely to give us justice regarding NSA wiretapping, civil asset forfeiture, CIA torture, or high-level fraud like with the misrepresentation of mortgage-bond risk or the recently reported Wells-Fargo crimes.
Based on what I currently know, I intend to vote for Gary Johnson. He's unlikely to win, but with Trump or Hillary, we've already lost.