I will prefer to outsource articles for writing, because it is very difficult to write article on daily basis.
If you have the time, I recommend you write the articles. You can get it proofread through some services like textbrokers.com if you think your article needs tweaking. You should hire a professional company who can submit manually to the article directories and have a good experience on that. Ask the company to create unique author accounts for you in the directories and then submit the articles under your account so that you can monitor the submissions and have full control over your articles. Most of the articles get rejected due to poor formatiing and embedding the links. A good article submission company can do that for you and submit according to the guidelines..
Try to write your articles, if your keyword is "very niche", you should write about general thing and include your keyword only in resource box. I'm very sure that you don't want to be beaten by your articles in Google results.
Yes If your article content write same topic of your site and keword relivant of you site this is good for your SEo way and your site improve shortly.
quality of article it's the root of the proces. article creation helps very much after submission on SERP.
I agree with most of the comments that said that the uniqueness of the articles will give you increase your SEO efforts.
When reading your post question came to my mind is will it be enough to submit articles? Actually it is one activity that required in SEO.
In order to get the most out of articles submission you should publish your articles in different places (goarticles,ezinearticles,aticlebase,buzzle, etc) You will have one or two backilnks from each article and it is important that your backlinks come from as many different places as possible. Article marketing is just a small piece of the puzzle....you have to do a lot more in order to compete in google for the first position.
At the moment, I write the articles myself. Since my purpose is to get backlinks, it's easy forme ot write for blogs, and then summarize for article directories. if I want to outsource, I might as well outsource all the writings.
try to make your self article and submit manually also make formatting and linking good. first read article term and condition after that post article so your article will not reject
My suggestion will be.. Write an article yourself. Then you can make variations by using a spinner like easyarticlespinner.net You can pick the top 10 directories and submit your article to them yourself or if you want to submit to more directories, you can outsource the job. Maybe to a freelancer in odesk.