JT8,
First of all, at the moment you need to be on the 320 to go on the 330.
And you won't get the 330 for about 5 years from joining on the basis of seniority.
And then we may get 757 guys going on the 330 as well in the future, or so a rumour goes.
If you join, expect at least 5 years of 757 or 320 before you get 330.