What's better for sales, a Facebook/Twitter channel or a blog?

In order of importance for driving sales (in my view)

1. Facebook

A Facebook company page offers many embeddable & interactive methods to engage or even realize direct sales through attractive, dynamic & to-the-point call to actions (web forms, e-coupons, quotation forms, surveys etc). In terms of engaging communication, Facebook has greater power in making discussions go and stay viral than Twitter, as it is far more personal & trusted than Twitter which sometimes allows for semi-anonymous, spam –like practices, making a "Facebook Like" closer to a word-of-mouth than a "retweeted" or favourited tweet! Also, Facebook has far more user-base per country or market segment than Twitter.

2. Twitter

Twitter can be used for multiple purposes, the least effective of which is “driving sales”. It does however help in creating new leads. Other more important functions are: creating brand awareness, driving web traffic, engaging existing customers, leads generation, improving brand image, increasing customer loyalty. This has all to do with the structure of Twitter (micro-blogging) & the fast-paced communications changing every second allowing little space for true engagement like the one offered by Facebook’s more lasting messages & multi-functional pages.

3. Blogs

Blogs are the "outsiders" in this comparison as they have a more informative text-rich way of engaging reader/customers that is not necessarily “social” in design, unless you make it one, by allowing commenting for instance. But, to the critical customer a company’s blog may be the first place to go to! Making a blog social through different social media widgets, add-ons & participation functionalities (Feedback, like Disqus) may make it more useful to sales than expected. A blog may contain attractive call to action features too, like embedded forms or e-commerce features that facilitate direct online purchase.

I think Facebook has an edge over Twitter. 

There are various criteria that differentiate Twitter from Facebook that includes education distribution, networking power, age and gender.

Facebook makes a natural fit for better commerce sales, as it has been shown that many Facebook users trust recommendations from users and brands on the most popular social network. However, Twitter is mainly made up of users that the average social commerce customer doesn’t know personally. Because of that, trust value decreases, also lowering the chances of regular sales through tweets.

Facebook.

Facebook is better, create your page, show your products/services and promote your page.

do not forget to place at least1 post / ad on your facebook page everyday to make it active

All of them will bring clients.And if you connect them to a formal website , it will be fine,or if you show your items on a paid market , it will be better.

Both require something to say as well as good and original content, I don't see why you need to choose between them.

You can have a blog as well as social media pages -they are not mutually exclusive and part of different areas of an integrated and holistic digital strategy

The most access way to customer is Twitter, but I need to select the target customers behaviours to find the the finest method.

Dear Ghadeer E.S. ,these all channels are working for the promotion of products only.

• Evaluate the available tools before you start. Facebook, Twitter, blogs, and have different attributes and audiences. In a nutshell, Facebook is for staying in touch, Twitter is for "breaking news," blogs are for telling the story, and YouTube is for videos. Explore each one carefully before deciding where to start. Find out where your customers are—look for groups within these channels that might be interested in your listings, like camera buffs or fashion mavens.
• Genuinely contribute to the conversation. Consider your target audience and how you can build your relationship with them. Budget time for keeping your presence fresh. You need to create original posts at least several times a week, and respond quickly to comments from your online friends and followers.
• Create a separate account for your business. Facebook rules require you to create a separate fan page for your business. Post about your eBay listings on your fan page, instead of on your personal Facebook page. Plus you'll look more professional!
• Start small. Start with one channel and build up your presence. Social media can be a valuable tool to enable online commerce, but it's important to focus your efforts on those activities that are most likely to provide a good return on your time investment.
• Listen and engage. Take the time to listen to what your social media fans and followers are saying about you on social channels. Responding promptly and engagingly to your customers helps you take advantage of the power of social media to cultivate loyal customers.
• Cross-promote your social media channels. Use your social media channels judiciously to cross-promote your content. Post a Facebook update when you have a new blog post, and include the link. Consider linking your business Twitter handle to your Facebook fan page so that your tweets are also auto-posted on your Facebook page—reaching both audiences at the same time. But be selective—you don't want to duplicate information on the same channel. Point your Twitter followers to your blog. You get the idea!
• Don't expect instant results! It takes a while to build a presence on any social media channel. As long as you post interesting new content on a consistent basis, visitors and customers will keep coming back for more.

i will rather choose facebook for publicity

• First it depends on what your product / service is.
• Second - what are your targeted segments?
• Third - based on the answers above, then you can make a decision.
• From my experience if your goal is to direct traffic to your website or blog, then social media (FB/TW/INST/PINT) can be used to link to your blog or website.
• I dont remember seeing blogs being used for sales, blogs are more personal and are more of a journal/diary/commentary etc.. maybe a blog can be used to write reviews etc. of product or service.
• In conclusion the goal is to get the content / message to the target customer and blogs / social media etc. are just different mediums to get that content / message across. They should all be interconnected and interlinked so that content / message gets across regardless of the device or social media / website /  blog / used.
• The only thing to be kept in mind is tailoring your content for each medium so you can post it in a long format in a blog / website; medium format for FB; short format for Twitter etc...