Writing file data for Android phone, or IOS

I dabbled in XNA a few years ago and wrote a windows phone game. Back then the recommendation was to use Isolated storage for saving files on phone devices. I was wondering if for Monogame Isolated storage is still recommended. I want to store player preference information (So text format). I might also score numerics, such as a players score. Can someone recommend the best file format for IOS and Android games written in Monogame?