should we use same apple id for ipad and iphone

The storage amount is linked to the account, not the device, so it will remain at 5GB no matter how many devices you sign in. Any devices which you want to sync your email, calendars, contacts and so on must be signed into the same iCloud account.

Think about it this way, when you buy an app, your apple id buys that app, not your device....so if you have 3 iPads, you can buy an app once and put it on all 3 quite legally. Same with books and music.

IMHO, the only reason for having separate ID"s is if they're for separate people.

Skydiver's comments are right on the money and, to that, I'll add that multiple IDs WILL result in nuisance problems and the worst part is that once you're there, there is no way out. Apple IDs can NOT be merged and purchase can NOT be transferred from one ID to another.

One possible use for separate Apple IDs is to have a separate ID associated with a particular device. This could be important with iMessage or Facetime, because if you associate all your devices with one ID, you will receive iMessages or Facetime calls on all your devices simultaneously. If you only want to do iMessage on your iPhone, for example, people could use the Apple ID associated with your iPhone, and the messages would not show up on your iPad. Obviously, this could be a good thing or a bad thing, depending on how you like to work.

For me, I have a single Apple ID, mainly because it is easier to keep track of my purchases and downloads. I also prefer to receive messages and facetime calls on all my devices, so I can choose which one to respond from.

Yes. If there are things you don't want synced you can fix that through 'settings'.

Incidentally, there are lots of useful comments in the 'More like this' legend to the right of your original post. Very useful source of info, Grace.

Hope that helps.

Thankew

Can we use same Apple ID to iPad Pro and iPad Air as well ?

Same principal applies. It applies across the board with iDevices.

I Manage an iPod touch, 2 iPads and a nano with one Apple ID