(1) I don't think you can reliably say after the first suck project. Some people are a bit slow at picking up new things, but become very productive after a while.
(2) Others pick things up super quickly, but never become super productive as the first group.
And of course lots of variations of people that don't fit neatly into either group.
I am in group (2) I think, but in my experience you really want people that become strong experts after a while. They are the ones I have seen do the best over the long term.
Salman Khan talks about this a little. He said one of the things they learned from the Khan Academy is that you can sort of group everyone into either "convex" or "concave" learners and they all basically get to the same level of competence by time T, and it's more a matter of do they plateau at the beginning or at the end.
He seems to be very careful about placing value judgements on which is "better", and he's also very careful to crop the graph near time T. His big push is to make sure that teachers understand that people that are categorized as "slow learners" actually often take just as long to get to the same level of proficiency as "fast learners".
(2) Others pick things up super quickly, but never become super productive as the first group.
And of course lots of variations of people that don't fit neatly into either group.
I am in group (2) I think, but in my experience you really want people that become strong experts after a while. They are the ones I have seen do the best over the long term.