Apps are really simple to install and uninstall, so why not just install all the main twitter apps (Twitter, Touiteur, Seesmic, Twicca, probably some more I'm forgetting) and give them a go.
They all do the same basic things, so it really comes down to which one you think looks nicest (my personal preference is Touiteur's darker theme, but Twitter's white/blue is also quite nice) and which ones are simplest to use (I wasn't a fan of the way Seesmic takes you to a separate page for each tweet if you want to interact with them, e.g. following a link).
Friendstream (and Peep) are perfectly functional, but they don't pack as many tweets onto the screen at once as other apps. Friendstream does have the very significant advantage of blending twitter and facebook updates into one feed.