Test three - Having chats
How about threaded conversations and direct messages?
People use Twitter for quick-fire conversation, both in public and in private via direct messages (which can be sent to anyone following you).
Twitterrific does neither (unlike the iOS version), but the other apps all enable you to view public conversation threads.
In TweetDeck you can display them in a separate column; Nambu expands them beneath a tweet, Echofon shows them in its drawer (in a rather fetching iChat-style) when you click on a conversation icon, and both Tweetie and Kiwi show a conversation when you double-click on a relevant message.
On balance, Echofon's approach is simplest and clearest, even if chats look nicest in Kiwi. Surprisingly, all but one client lists your direct messages linearly in reverse-chronological order.
Tweetie is the odd one out, enabling you to access them by contact, which is much clearer, although Nambu at least enables you to view sent and received direct messages separately.
Test four - Doing searches
Is searching tweets simple and can searches be saved?
All the apps on test, excepting Twitterrific and TweetDeck, enable you to use a search field to find related tweets, which are then displayed in the main timeline window. Terms you want to track can also be saved, although methods vary.
With TweetDeck, this is the only means of making a search, and each becomes a separate column – great for tracking, but annoying for one-off searches. The other apps all enable you to flag any search made as a favourite that you can return to later; and, aside from in Echofon, new results are highlighted when your feed is refreshed.
There are differences in search setups, though, and we found Nambu's icons awkward, but Tweetie's interface was very clear. Kiwi takes a different approach, enabling you to add searches as separately defined 'accounts'. This provides you with more scope for complex searches, at the expense of cluttering the account-switching menu if you've many searches stored.
The winner / Echofon
None of the apps here is poor, but three quickly fall out of favour. Twitterrific is too basic and fiddly, and TweetDeck and Nambu are too complex for their own good (although TweetDeck's worth considering if you need to track, manage and post to a large number of accounts simultaneously).
Of the others, we like Tweetie a lot – its message threading is great – but it lacks support for some recent Twitter features. Its developer now works for Twitter, and a revamped version is likely imminent.
Today, though, the title fight is between Echofon and Kiwi. Despite its small post area and occasional refresh issues on switching accounts, Echofon edges it, but if the minimal interface isn't for you, Kiwi and Tweetie are worthy alternatives.