Twitter is always looking for ways to improve its service and to give us more. But, the social networking site probably didn’t have this in mind. According to a new Onavo survey, among Twitter apps for the iPhone/iPod touch, it is Twitter’s own that hogs up the largest amount of data. And, for 3G Twitter users this could significantly impact the monthly cell phone bill.

For most, a Twitter app serves one underlying purpose; to post and read tweets. However, not all clients that provide this service do so equally.

According to Onavo’s “Twitter on iPhone: By The Numbers” survey, Twitter for iPhone uses 193.2 KB, based on the average results gathered from “the iPhone data counters, using a simple scenario.”

This compares to 163.2 KB for Echofon and 112.8 KB for Tweetbot.

The most efficient Twitter app for iPhone is TweetDeck, which uses just 86 KB. Ironically, Twitter recently purchased the company behind TweetDeck for at least $40 million.

Among all Twitter iPhone users, 65 percent use Twitter for iPhone, compared to 8 percent for both TweetDeck and TweetBot, and 4 percent who use EchoFon. Another 15 percent use another client else.

Take a look:

Twitter Data Usage Survey

Twitter Data Usage Survey

Note: The graphic is easy to read simply by click on it (once or twice, depending on your browser).

Onavo, whose free app helps iPhone owners shrink their 3G data usage, claims it helps users eliminate an additional 65 percent when using TweetDeck.

Since more KBs could lead to higher bills, 3G users especially should consider this survey when deciding which Twitter client is best, at least on their wallets.

What do you think? Leave your comments below.