When I write an article the images always have file names that match the content of the image and an important keyword of the article.  The alt attributes are more detailed because they  provide information to screen readers.

I believe that the names of your image files and the alt attributes are small optimization elements that will help rank a page.  It might be enough to move you up a position or two if you are deep in the SERPs, but if you are in a battle for the top three for a competitive term then authority is going to be far more important than the sum of the small optimization elements.

I would write one authoritative article that is the best on the web for this topic.  It would have lots of high quality photos and be clearly divided into subheadings so that a person scanning can find what he is looking for.

An article that immediately impresses people with images, breadth and length has a better chance of being shared than a large number of articles that cover only snippets of the topic.

Long articles also pull in nice amounts of longtail traffic because they have a huge diversity of words on a page.

**If I copy description from my web and paste to Youtube description, this is duplicate content for Google **

I agree with Stelios and am very pleased to see that Christy endorsed his answer.   Please don't do this!

We have a few dozen youtube videos that demonstrate how some of our products are used.   We write a big article on our own site about each of these products with the video embeded.   On youtube we post a very short - no duplication description.

Now when you search for these products on Google, our "demonstration" article ranks at the top of the SERPs... and our youtube video is lower on the page.   I am betting if we duplicated our own content on youtube that the article on our website would not rank in the SERPs because the page on our site and the page on youtube would have identical content.

Before you redirect... it could be much more profitable to run these sites separately.

A proper analysis could take a few minutes to a few hours to decide that they are not worth much... or it could be worth a lot of money to have someone who knows what they are doing flip these sites and convert them into valuable assets that earn many times more than what their previous owner was doing with them.