A: John is a better player than Martin, isn't he?
B: Oh, yes. _______ the match tomorrow, I expect.
1) He will win
2) He is going to win
Which one is preferable here? (Me: #1 is better than #2.)
The "I expect" certainly makes "will" justifiable. (Without "I expect," "He will win the match tomorrow" would sound like a prophesy .) I don't have a preference for either one.
If "I expect" appeared at the front of the sentence ("I expect he will win the match tomorrow"), I would join you in preferring "will." But it doesn't appear there; it appears at the end.
A: What do you want to be when you grow up, Stevie?
B: _____ a scientist. That's what I want to do, anyway.
1) I will be
2) I am going to be
(Me: #2 is better than #1 here.)
I agree with you here: "I am going to be a scientist" works better than "I will be a scientist." Using "be going to" communicates intention, and that is appropriate in this context.