Evan, although it is very tempting to try to automate posting messages to every social app you want to use, please remember that they are all different and should be used accordingly. First of all, ask yourself what you are trying to attain by using each of them. Is it about posting links to your blog? Or is it more about active involvement with your friends or customers?
If you want to use each platform to its full potential, you need to spend some time with every one of them individually. For example, while Twitter is great to automate posting of links to articles on a blog, posting short, original content and getting involved in conversations directly on Twitter is a must if you want to be regarded as someone worth attention. A Twitter account that is only used for broadcasting links is just this - a broadcast, one of many similar accounts with nothing original. In the meantime, you can have a really fascinating exchanges of 140-character long messages with people that are somewhat connected to you or the subject/product/service you post about or make a brand of yourself by posting brilliant, Twitter exclusive reviews that are not just shorter versions of what you have written elsewhere but are engaging of themselves.
It is similar with Facebook. It gives you lots of tools and ways to connect with others but the character of the platform is different. It may be more private than Twitter but it allows you to be seen on many walls when somebody "likes" your page or befriends you.
I know this is not a direct answer to your question but maybe there are deeper questions to be answered before you decide on the degree to which you want to automate things (and therefore make your content more generic and less aligned to each application)? Which platform serves your purpose best? What is the priority between them? How can you use each of them to their full potential? If you know answers to these questions, it will be easier to decide which app you will provide with the most of the original content and which one will only serve as a broadcasting machine.
Keep in mind that it is not always best to post every update from one service to another. People may think that you try to engage them the easy way, without a real effort. This may not be true but perception is king.
I hope it helps.