Micro-blogging is a form of multimedia blogging that allows users to send brief text updates or micromedia such as photos or audio clips and publish them, either to be viewed by anyone or by a restricted group which can be chosen by the user. These messages can be submitted by a variety of means, including text messaging, instant messaging, email, digital audio or the web.The two most prominent systems in this field maybe are Tumblr and Posterous. I have tried both systems and each have their own advantages and disadvantages.
The content of a micro-blog differs from a traditional blog in that it is typically smaller in actual size and aggregate file size. A single entry could consist of a single sentence or fragment or an image or a brief, ten second video. But, still, its purpose is similar to that of a traditional blog. Users micro-blog about particular topics that can range from the simple, such as "what one is doing at a given moment," to the thematic, such as "sports cars," to business topics, such as particular products. Many micro-blogs provide short commentary on a person-to-person level, share news about a company's products and services, or provide logs of the events of one's life.
CustomizabilityUpdate: Custom themes already comes to Posterous. More details in here.
Tumblr definitely wins in this aspect. You can install pre-made themes and templates into your tumblr blog or you can make your own. Moreover, you can add scripts just like google adsense, mybloglog, google analytics into your tumblr blog.
This is the main limitations with posterous. I once noted that this is one feature they were supposed to offer in the future, but revisiting their FAQ--it's not there anymore (their plan to offer the ability to change your theme).
Favicon-wise, you can change in at your tumblr blog but not in posterous. You always have to deal with that regular posterous icon as your favicon.
Think about it, your blog at posterous looks like any other blog around hosted by posterous as well. How do you like that?
Commenting SystemCurrently, tumblr does not have a built-in commenting system, while posterous have one. I can't speak about the effectiveness of the anti-spam of the latter as I don't really have a popular blog in there that can be able to solicit a lot of spams.
However, you can always install Disqus into your Tumblr blog and instantly you have a working commenting system. It has also been tested against spam as many popular blogs are utilizing the same in their popular blogs.
Ease of PostingBoth services offer posting by email. (Unfortunately, both also don't know how to insert line breaks, if there are any in my original email, to post to my blog). But Posterous handles photos better especially when you have attached more than one photo. It auto arranges them into a gallery-like post that really look nice.
Both services also have a bookmarklet, but I liked Tumblr's even better. It's quicker and more responsive. It allows you to classify your post on the fly as to whether it's a video, photo, audio, text, quote or link.
Custom DomainsBoth offer custom domains. However, I believe Tumblr handles redirection very well than Posterous. If you have a top level domain name (e.g., domain.com), any request for www.domain.com are duly redirected to domain.com in tumblr, while in Posterous your blog is accessible at both www.domain.com and domain.com. This makes it anti-SEO as Google and other search engines think you have duplicate contents both at your main domain at domain.com and at a subdomain www.domain.com.
Storage SpacePosterous explicitly states in the FAQ that you are limited to 1GB of upload space for all types of media files (including documents). In Tumblr there's no such provision. You decide.
Facebook IntegrationBoth have an available third party app (I don't know with posterous maybe it's not 3rd party) that can enable you to autopost your blog posts to facebook.
OthersI can't think of anything anymore. But I'll update this post once I encounter any other differences (or even similarities) worth mentioning. If you know of one, please feel free to post your comment below.
ConclusionHands down, my vote goes to Tumblr. The most selling point for me is the customizability and the custom domains feature.
Check out my tumblr blog here.
What about you, which microblogging platform do you prefer (aside of course for twitter, as twitter is definitely not in the same league as these two, much less is wordpress)?
Update: I discussed more about domain mapping here.