[brudgers]

It depends on the details. There is no formula that is always better.

But the reasoning behind landing page first is that it focuses on engaging users/customers because some (most?) people will avoid the risk of rejection that comes from engaging potential users. Instead of building something based on people's actual problems, they build based on imagined problems.

Which points to a third approach: build something that solves one of your problems (or a problem for someone you know).

Good luck.