Is the first sentence more formal than the second?
Two more people are needed to complete the team.
The team needs two more people to be complete.
No, it isn't. But if this was a notice on a board, you might choose the first, because it emphasises the two people needed rather than just saying something about the team. Speaking to a friend, I'd probably use the second. But speaking to a group of potential team members, I might say the second. That's not really an issue of formality.