It really depends, actually. If you're target audience can be found more on Facebook than Twitter, then go for Facebook, and vice versa. But personally, I'm more for Facebook, it has more tools I can use for marketing, compared to Twitter.
You don't have to choose one versus the other. You should promote your website/business using both. Use Facebook to create a fan page and post contents on your page. Use Twitter to post messages and share content.
One of the advantages of Facebook is that it doesn't cost a lot of money to advertise on the platform. Twitter however requires way more money.
Which one is user friendly?
Both, in a different way. Twitter is public and hashtag based.
Which one is useful for us?
It depends a lot on your audience and what they need.
Which one is reach people easily?
Eh, well. It differs. Facebook is on-page and Twitter will get you more visits, but it really depends what kind of the users you have.
Desktop based are usually more available to visit your blog.
Android not. Well, in my case.
I constantly advise you to remove your idea of purchasing Facebook Likes because it's not a great idea. But I consult you to use some tools and Facebook Ads to get tons of Facebook Likes.
Both are great, but personally I've seen more success with Facebook. It actually all depends on your target group and your service/product.
I believe that Twitter works better when you have an already well known brand or if you're connected with some influential people. Facebook is better for reaching people and presenting your thing to them. You simply have more means of interaction that on Twitter. The latter is my choice.