You may not love Safari, the default browser on the iPhone, iPad and iPod touch. And you wanted to change your default settings of your iOS browser. There is no such settings but a jailbreak tweak called Browser Changer will let you do that. The tweak is free and downloadable now via Cydia.
Once you’ve installed Browser Changer on your iPhone, iPad or iPod touch, you can now select when browser you want to open when you click on any link inside any particular app or email. Browser Changer will also overmap Maps and YouTube applications when relevant links are clicked, hence opening the browser of your choice for that matter.
You will, of course, need to have a jailbroken iPhone or iPod touch to install it.