Realgud points everyone. I've been swayed and forced to change my vote again!
The major difference between Nyquist and Tatar is that Nyquist is a goose, and Tatar is a Mexican water bug.
Now the thing about geese is that some can lay golden eggs, like Gus did during the 13-14 season. However, to lay golden eggs, geese have to be loose. Hence the phrase "loosey goosey". Because geese are not always loose, a goose like Nyquist will be streakier from time to time.
Being a Mexican water bug, Tatar is obviously more lively and quick with the puck. But the main advantage of being a Mexican water bug is that it is a made-up insect that only exists inside the mind of Mickey Redmond. So basically the sky is the limit on Tatar's potential and what he will develop into. Don't ask me why Mickey's made-up bug is Mexican.
I know it's boring nerdy science stuff i got from a spread sheet, but the facts are there. Each has their strengths and weaknesses.