To get your keywords on higher position which will give you quick result? DIRECTORY SUBMISSION or BLOG POSTINGS???
That would depend on the quality of your blogs. If you happen to write for some High-PR blogs with loads of backlinks, that would be the most effective way. But why limit yourself to one method?
Don't waste your time submitting to directories other than DMOZ and Yahoo Directory. In order to improve your SERP you need real links (blogs, forums, sites, etc.)
As mentioned above, you should diversify your strategies and use a few techniques. That way you are less susceptible to search engine algorithm changes that try to limit the effectiveness of a certain technique. It is very difficult to get any competitive rankings using just one technique.
i would not suggest to pick from directory submission and blog posts only. dont just pick one specific link building method and stick with it. if you are in a competitive field, you need to leverage several methods of link building to make the best out of it
I agree with this but why not trying combination of this with links in other sites, directories, and articles written by you and submitted to article directories?
Directory is most effective tool then Blogs, However blogs also play important role, so do both things to get results fast