Here's how I use my iPad (with WiFi and 3G). I have about 100 songs and no films on it and it still isn't enough; not by a long way.
1/ At home. Use Wireless network
2/ At Work. No Wifi and not allowed to connect it physically to any network and no mobile telephone network available. I use it as a stand alone tool alongside my laptops, PCs, Servers etc. Great at meetings, particularly where there is 3G access. Great for presentations, and films to show at work.
3/ Out and about. Despite the fact that I live in the third largest city in the UK, most of the time WiFi is unavailable; as is a 3G connection. So, stand alone iPad again.
4/ Travelling. I travel light with a carry on bag only. With a camera I have limited space and weight (often times 8KG maximum). The Macbook Air is great, but has limited battery time, and is not as good as an iPad when travelling. many places I go there is no WiFi, no mobile network and limited electricity - quite possibly a few hours a day - if lucky.
I take photos in RAW & JPEG format. 97% of the time there is no access to the cloud and a very, very poor to nil mobile telephone connection that can be used for data transfer, (whether music, data or movies). I have the cloud, with all my music etc. It just about is never used. An iPad with larger memory would be great for me. I also do not wish to pay £3 million per kilobyte of data (exageration, but hopefully you get the idea) for transferring data when it is possible.
I am able to think of other situations where a larger memory is good, not just for me, but for other people.