Question about Icloud Drve

Yesterday I shut off Documents and Dat in my settings and then I couldnt turn it back on the option went POOF. I read that you should the use ICloud Drive. (Which has been off since I upgraded to Iphone 6 plus and and new Ipad. Although it was set to back up to the icloud. I generally back up to my computer threw Itunes. I dont pay for storage.... I am trying to figure out why I would need Icloud Drive on. Does it burn threw battery usage? I habent noticed. Also I use google Drive for documents and things. It seems the contacts, calender, reminders and the notes are all sync across devices whether Icloud drive is on of off. (because my default is google) The only thing I notice that is affected are my keyboard Shortcuts? Is that a true statement? I can not seem to gasp the importance of Icloud Drive would be for me??? ANyone? Also I signed into it on my pc this am and it was my SONS photos on there not mine. His photos were set to sync but I have since changed that. I just pull the pictures manually when the device is hooks up to my computer.

Can someone explain to me is it better to have it on or off? And is there anyway to get the documents and data back on? Because it seemed the keyboard shortcuts work with that? NO?

Thanks.