Apparently some people out there haven’t quite caught on to the microblogging craze, or are a bit confused about the differences between the two. Here’s a somewhat lighthearted look at the two in a no holds barred, knock down, drag out fight.
Lets get ready to rumble!
In the light blue corner, the reigning champion - Twitter.

Twitter has been around longer and has a large userbase. The number of clients, addons, extensions, related websites and methods of access is impressive. Lately though, the champ has been stumbling, suffering from extended outages and downtime.
The various clients available for Twitter, when working, are a great alternative to the web interface. My current favorites for Windows are Snitter and Twhirl, but both can be buggy at times. There are also multiple plugins for firefox available. If that’s not your cup of tea you can get at Twitter from IM or SMS. If you’re a fan of text messaging, this can be a fun way to occupy your time while riding the subway to work.
There are a large number of websites that extend Twitter’s functionality. Tweetscan lets you easily search Twitter for tweets containing certain text. Twitter Karma helps you keep track of who is following you and who you are following. Twitterpacks help you find people with the same interests as yourself. Tweetstats reports on your usages, and there are a host of other websites as well.
Reliability is an issue with Twitter, and drives people to Pownce during the downtime. Twitter officially broke up with Joyent recently, and some of the stability issues may improve. Time will tell.
In the green corner, the cagey up and comer - Pownce

Pownce has just come out of beta and has some catching up to do with regards to the number of users. A reasonable number of people have signed up, but a majority of them don’t use it much. Activity has picked up with the recent Twitter outages, but it is still far behind.
Pownce goes beyond the realm of just text and allows you to post pictures, videos, music and other files easily. Also, it’s remarkably simpler to add links just by clicking the button, compared to the usual cut and paste then tinyurl process with Twitter. Most of the videos are just youtube viral videos, but it’s a fun way to share amusing vids with friends. The ability to share photos is very cool. I threw up a picture of my dog, but there are some gifted photographers out there who frequently share some excellent material. I personally enjoy these very much. There is a lot more creative stuff being shared around on Pownce compared to the Twitter’s pure text and links.
There are a few fan created and third party applications and extensions for Pownce, but for the most part Pownce is still in the infancy stage for this category.
One cool feature in Pownce is the ability to group friends in sets. This can be useful when your friends list starts growing and you need an easy way to sort or separate them. I wish Twitter had such a feature.
Also, if you wish, Pownce has plenty of room to provide all of your other contact information like Twitter ID, Flickr, Facebook, IM, email, blog, homepage. I find this a handy way to find people on other networks. I just go to Pownce, click their profile, and presto, all the info I need. Currently Twitter just allows one link for each user.
Pownce has a nice interface for finding friends. It can easily scan your Digg, Facebook, Twitter, Flickr, GMail, Hotmail, AOLmail and Yahoo mail contacts. Twitter will only search email contacts (from the same 4).
Point by Point Comparison
Number of users/activity: Advantage Twitter, by a large margin. Pownce may slowly creep up, but Twitter has a huge head start.
Third party support, addons, and extensibility: Advantage Twitter, by a lot.
Reliability: Advantage Pownce. Twitter has been having problems lately and it’s trying people’s patience.
Accessibility: Advantage Twitter. Web, IM, Txt and local clients provide many options for getting connected.
Flexibility: Advantage Pownce. Videos, pictures, music, easy linking, and text sans the 140 character limit.
Friend Finding: Advantage Pownce. Both let you search by name, but Pownce has more options for importing from other services.
Tally
That’s 3 for Twitter and 3 for Pownce. OK, the numbers are misleading. Twitter wins, easily, if only because it’s what people are using right now.
In the end, it all boils down to what you want. If you want to share a variety of media types, you need Pownce. If you want more access options, Twitter is the way to go.
Personally, I’m still using Twitter most of the time, because that is where the action is. I also use Pownce on a daily basis and enjoy the different kinds of content that pops up there. If you into social networking and web 2.0, you should probably start using both.
Before long we’ll start seeing clients that aggregate both Pownce and Twitter, and by then there will be no reason not to enjoy the benefits of each.
-Jeff