With 2 languages, is better for SEO to use 1 website or 2?

What is better for SEO?

- 2 separate websites, 1 for each language?

- 1 website and give users the option to select the language?

I'd say is much better to have 1 site that offers user the posibility to change the language.
There's a lot of reason for doing this,but some of the main ones are:
-Branding
-Site Authority

Maybe one site. There was a theme on multilingual site gets higher PR. Probably..

Here are some reasons to have just one website:
1) You will spend less money for development and advertising..
2) You can focus all of your traffic on one website and have the benefit of cross-promotion.
3) You can just as easily syndicate your content across multiple mediums using social media sites.
4) It is entirely possible to focus your organic search results to come up on a variety of keywords.