What will be the best option for two different language blogging?

I want to make a blog for a niche. But I am willing to post in two different language. What will be the option?

1. Post same topic in

Language 1 - Post
Language 2 - Post

So there will be two post with same topic in two different language.

2. Make a subdomain

Language 1 - Main site
Language 2 - subdomain site

So I need suggestion what option will be the best? As I am intend to apply for google AdSense.