I'm not sure what functional you mean unless you mean Twitter for iPhone has manual quotes which Twitter for Android does not. But Twitter for Android has this:
1. It can show pics right on the tweet itself. Sorry but no other Twitter app on the iPhone does that, and the only other Twitter app that I have seen that does this isn't on the iPhone, its Ubertwitter on the Blackberry.
2. You can sync your Twitter followers into your phone contact book.
3. It has push notification. Other iPhone Twitter apps actually have push notification such as Echofon and Twittelator, but definitely not Tweetie/Twitter for iPhone.
4. It has an onscreen widget. I don't have to open the app itself to read tweets.
5. It has streaming sync. It continues to update the home line even if the app is not up.
Apple's copy and paste mechanism is better than Android's, but not much better if you really used them both. Actually when it's Select All, its faster on Android.
Copy and paste is trivial superiority because the iPhone OS doesn't do a good job of passing output from one app to another. Simply said, most iPhone apps don't and when they do, you have to build that capability into the app and to specifically address another app. That's how only Seesmic for iPhone can send a tweet to Evernote and only they can do it, but not Tweetie, not Twitterrific, not Echofon, not Tweetdeck and you name it. But this is old news on Android because every Twitter app from its inception has this capability ("Share Tweet") because the pipe is universal and modular. This pipe lets you send a Tweet to Facebook, other Twitter apps, Google Buzz, LinkedIn, Foursquare, Evernote, Gmail, SMS... you name it, as long as the social networking app for that particular service is installed (modular construction).
Another example. You see a link in your iPhone Twitter app. You click on it. Where does it send you? Mostly it sends you to a mini browser inside the Twitter app itself, with the option to Open Safari on the corner. If you open Safari, the Twitter app closes and you have to manually open it again. Likewise with Maps info. It sends you to a mini Map browser with the option (on some apps only) to open the Google Maps app.
On Android, if you click on the link, it will either send you to the default browser or a menu that will list all your browser options...Dolphin, Skyfire, Dolphin HD, Infinity... You browse on the real browser, not the mini one, and the return key immediately sends you back to the Twitter app, which is never closed. Likewise, the map location can be sent directly to the Google Maps app, not a mini browser, where you have full access of the Map functions from Street View to Buzz.
Unlike the mini browser that's built in to the Twitter app, the Android browsers themselves can share the link further, to Twitter, Facebook, Evernote, and so on and on through the modular universal pipe.
That's why I can do a sequence on Android which I can't do on the iPhone.
Twitter app -> Link to Android browser -> browse more pages on the Android browser -> share that page back to Twitter as a new tweet. (Yes, the Dolphin browser has built in URL compression and GMail formatting, meaning it turns the title of the page into the header of the tweet without manually typing the title).
As for Facebook on iPhone, it has chat, which is what its better on the Android version. But the Android version has an onscreen widget which can display Facebook posts without opening Facebook itself. It streams Facebook without opening the app. Furthermore, Android has been syncing Facebook contacts into the phone Contacts book for many months now, which iOS is only offering just now.
I can tell if there is a Facebook update, like posts or new pics, from a contact simply by browsing my phone contacts book. On Android, you can even open the Facebook app and contact reference directly from the contacts book view.
Honestly, Facebook on the iPhone has its annoyances. You see a notification on the bottom. You click on it. What does it say?
Mr. Joe Shmoe commented on your Status.
(That's it, you have to go to your Wall to read what he wrote. Or his wall. Some menu navigation there).
Facebook On Android does it notification like this:
Mr. Joe Shmoe commented on your Status.
"Hey did you watch the LOST finale? What do you think?"
BTW, Facebook for Android has updates that did include Inbox.