I now have an account on all three mini blogging services. First off, all 3 are basically extremely easy ways to communicate with your friends. For example, I may post “Anyone out there know how to use XYZ?” or “I am currently working on ABC”. The idea is that these short messages are pushed out to your friends to read. If anyone has used Facebook, they are the same idea as Facebook status, but can be updated from anywhere, and is much better in my opinion. But that still does not answer which one is better.
Ease of Use: Twitter wins this one hands down. Not only does it have a simple interface, but it has an API, and can be updated via plain, old IM. Jaiku comes next, as to use IM to update, you have to use a 3rd party interface such as IMified. Pownce, the youngest of the bunch and still in Alpha, has no API and requires use of their website or Adobe AIR client.
Features: Twitter comes in last, with only basic one way messeging support. Jaiku comes in first due to its ability to import any RSS feed, plus do everything Pownce does so far.
Network: If you are looking to see which service has the most people who update often, the award would go to Twitter primarily due to its IM interface. Pownce comes in last since it is invite only still.
Overall: In my opinion, Twitter still wins purely on the fact that it will let you update and send out updates via IM. Pownce comes in second due to its nice looking website and desktop program. Jaiku comes in last since I cannot get updates on my desktop and being primarily designed for cell phone use. To sum it up: Twitter > Pownce > Jaiku
I have limited invites for Pownce, so if you want it, post in the comments and I will invite the first poster who should thus invite the next guy down the line. Jaiku and Twitter can both be signed up for on their respective sites. Feel free to add me on any and all of them. My twitter is kurtisnelson and my Jaiku is kurtn My Jaiku is a simulcast of my Twitter. My Pownce is kurtn and will not be updated very often until they release an API.