Should multi-language site using multi-site architecture have default language in base site?

I am setting up a multi-language site using wordpress multi-site and wanted some feedback on the best approach/best practice.

I will have the following languages: en, sa, de, ru.
en is default.

Should the domain.org by default be English, or should domain.org redirect to domain.org/en?

Create a subdomain for each language, set the main site to English. Then use the plugin Multilingual Press to chain these subdomains together. It has an option to redirect the visitor to the correct single page too if it is translated on another subdomain (not sure if that is part of the free version).

Subdomains are slightly better than sub directories for SEO because Google will detect the correct language with … a higher probability.