If you are a team, incorporating is important to clarify ownership. You dont want to have to figure that out later, after you are successful. You can also do that with a document among the team. But don't wait too long. It's amazing how everyone's recollection of an oral agreement is sincerely completely different a few months or years down the road.

If you are an individual, it's not that big of a deal either way. You can wait till you get traction to do it.

If you hope to raise VC money some day, I'd suggest creating a delaware corporation and not an LLC. But it isnt that big of a deal either way.

There are of course tax questions, liability concerns, etc. Talk to a professional (attorney, accountant) if you're not familiar with these.