I was curious as to whether the landing page of a social mobile app should be built for a user to signup or login.
This example lands on the app's signup page with an option to be redirected to the login page, and this example does the opposite.
I would appreciate a clarification on which is considered 'wrong' or 'right', and on which occasions each is acceptable.
Think of this; what type of users will most likely visit your website? Returning or new users? Design your landing page to fit the primary type of users visiting your page.
I think new users will visit your landing page more often if you use some sort of 'stay logged in' option for users, but that's just an assumption.
I would assume both types of user will visit your site and I don't see how having two options would be detrimental to either.
If you just have one option, say login, then new users have no way of signing up
"Form Follows Function", or as we say in UX "Design must solve a purpose".
That purpose, is defined by the Company at its growth stage for you. For example, in an e-commerce firm, some sites will have the search-bar in near same color as background (sort of blended in), that's because their catalog is less and Browsing is main method in user-journey. The business also depends on users getting accidental discovery of new products in their browsing path. Where as other big giants like amazon, have search bar over an inverted color palette, improving its visibility as its one of the main methods for a user to reach his desired product in a large catalog.
So, for a new app/service, the path may be to promote SignUps to improve conversions, where as for something in growth stage, it would be Log-in to promote engagement.
So if users are migrating from an existing web service, like Facebook, then lead with login. If its a mobile-first app or most users of web have already downloaded and installed and all the fresh downloads are going to be mainly by new users, lead with "Sign-up"
So the one possible answer is "Whatever suits the business requirement"
There may be other answers, each pointing to a different data set. In absence of Data, this is one to start with.
If you check out Twitters landing page (or even Facebook), for instance, you'll see the main point is the sign up form not the login form.
Like Nick said, depends if they are going to remain logged in to a service or not. With a social media site for instance you would assume more often than not the user would stay signed in unless they were using a public computer, someones phone etc. in which case they would be signing in/out (But I suppose those scenarios would be less common in comparison).
It depends on the type of users (new or returning) but both the options should be easily and clearly available to the users. Also it would be easy if user can easily switch between sign-up and sign-in screens without delay. A simple example would be using tabs for each functionality and make it prominent.
