Web-based HootSuite is unabashedly directed toward those who want to use Twitter for business purposes; its browser tab caption reads "Welcome to HootSuite - The Professional Twitter Client."
What does TweetDeck do?
Like Seesmic, TweetDeck, and several others, HootSuite works via columns; you can have separate columns for your home feed, for your replies and mentions, for groups, and for any search that you care to do.
Hover your cursor over a person's tweet and you get icons that let you mark it as a Favourite or create a direct message, a reply or a retweet.
You can monitor several different Twitter accounts (but not your Facebook account), do either a keyword search or a general search, and assign users to groups.
What's cool about TweetDeck?
If you like Web-based Twitter clients - for example, if you use more than one computer and can't install an independent Web client on all of them - HootSuite is a good choice.
What I especially liked was HootSuite's simple, elegant layout, which made it easy to find and use most of its features - a distinct advantage when you're not all that Twitter-savvy.
And HootSuite manages to avoid a problem that plagues most other column-centric Twitter clients: If you're trying to monitor more than three or four columns, you end up with a virtual window that stretches well beyond your display's capabilities.
HootSuite's use of tabs to separate out sets of columns means that you can easily access - and see - a wider variety of searches and feeds.
HootSuite also has some nice extras, such as a "Send Later" button that lets you schedule your tweet rather than just send it immediately.
HootSuite also makes it very easy to get information about users by clicking on their names; you get an easy-to-read pop-up that offers info such as their follower/following and their description.
This is sleeker than a similar feature offered by TweetDeck, which creates a new column for that data.
If you're looking to aggressively promote yourself or your company, there is also a direct link to Ping.fm, a service that allows users to send out their tweets to multiple social networking sites.
Finally, HootSuite uses its own URL shortener, Ow.ly. Like the third-party Bit.ly URL shortener service, it enables users to not only shrink long URLs, but also check how many people have clicked on that URL as a result of their tweet.
What needs to be fixed?
To begin with, the folks behind HootSuite should learn that good word of mouth can't be forced - to try a beta of the 2.0 version, I had to send a tweet supporting the product. If I hadn't been reviewing the service, I would have been strongly tempted to decline the honour.
And there are features that still need tweaking. For example, if you want to create a group, you have to type in at least one username, which can be a problem - usernames can be strange enough that it's difficult to remember them exactly.
Once you've created the group, you can drag and drop users from another column to your group column to add them to the group, but that still means a search for all the users you want to include. Mixero, which provides you with a list of your users, makes creating group much easier.
For a Web-based Twitter client, HootSuite offers some nice features and a few that other free Twitter clients don't, such as a convenient way to get a hit count through the Ow.ly feature and tabbed pages. If you prefer a Web-based interface and are using Twitter as a way to promote a brand or some other commercial venture, this should be on your short list.