I like iOS one thing: I can type Vietnamese in iPhone, iPod Touch, iPad quickly without install additional app. Android is not.
For Android version before 4.0, you must install a third party app to type Vietnamese. It's scary. Some apps ask for unnecessary permissions like reading your contact, your account info, your SMS message,... When I installed some trusted apps to type Vietnamese, as a precaution Android warning me for possible security breach like keys log. So I uninstalled them and used the built in Google Keyboard. Since it do not support any popular input method used by Vietnamese like Telex, VNI or VIQR, it's hard to use and slow. For example: To type letter 'ê', I can type ee (Telex type) as in iOS but for Android Google Keyboard, I must hold a letter e to see it displays other characters, select and drag letter 'ê' to an input text box.
I hope Google should catch up with Apple in support Vietnamese input. There are a lot of Vietnamese in the world using Android-based phones and tablets.