The developers of QR Reader for iPhone got it exactly right. It’s the quickest to scan out of the five apps; it has a huge range usability and sharing options; and it also looks good.
When you read a code, the app will show you a “details” view which allows you to launch another app to open the information, except text and URLs, which both open within the app itself. For URLs, there’s a built-in web browser which cuts out the need for launching Safari. There are ads within the web browser view, but that’s a small price to pay with an app as nice as this.