I usually only use Chrome for CC on an iPad. The main reason is it that automatically populates your user/pass without having to type it in every time.
This is also the same reason I use Opera on an Android phone although you have to press "forgot user name" and right after that, it will automatically populate the user/pass.
GoranZ brings up a very exciting feature w/ TamperMonkey and Android w/ using scripts. I remember not too long ago reading an article where you can run Android on the iPad via a program although i can't remember what it's called but it seems like it's similar to Parallels on Mac. And if that's the case, hypothetically, you should be able to run Android on your iPad, install Firefox, TamperMonkey, etc.
Curious to find out if it works. I'll touch base if I end up trying it.