One difference is that Perot appealed to men, and Trump appeals a lot to women. He will be a power broker and could very well cause a split in the party due to his social liberalism. This will be a dangerous game.
I don't see the TV celebrity, billionaire casino owner convincing enough voters to take him seriously enough, for him to have a real shot at the nomination.
However, I do like the fact that he's forcing some taboo subjects into the main arena of public debate. He's uniquely positioned to do so, as he really has nothing to lose if he's attacked by the left.
The MSM can't hurt him, so he's free to speak his mind, and he's so visible, that millions of Americans will hear him. He's doing the right an enormous service by breaking the ice on these subjects. We will see which Republican hopefuls actually have the cojones (or ovaries) to take advantage of the opening he's provided.