Hi and welcome to the Forum!
While 16gb may be fine for your iPhone an iPad I believe is a different matter entirely. There is so much more that you can use your iPad for, the size of the screen is just superb for viewing movies and photos. Do you like to watch movies? As these will fill up an iPad very quickly. You will use your iPad for tasks you're not even thinking about now, I have my home inventory on mine, also my book library as well as hundreds of ebooks, recipes and there are a myriad of apps to discover.
I have a 3G iPad as I travel frequently and do not want to have to rely on public or hotel wifi. I have a prepaid sim and I just top it up when I know I'll need it, when travelling overseas I'll just buy a new sim card with data and away I go, its very simple. But there's more to the 4g than just being able to connect to the net, it is the only way to have true GPS and the size of the screen is very good for this task and you don't even need to have an active sim card for this to work for you. I love going for long drives and I use this feature frequently. I have 64gb and I've used half of this right now, if you're good at managing your iPad you can leave a lot of apps, movies etc on your computer and just swap out what you will be needing, but I like having it all available and don't want to worry about space being an issue. I believe that you should go for the biggest you can afford, but that's up to you. Hope this has helped you.
The IPad Forum is a community of members from all walks of life and from all over the world coming together to share our experiences and to help each other learn about this wonderful piece of technology the Ipad. There is a wealth of information already here in the many threads we have so doing some searches will answer most of the questions you have. If then you cannot find the answer you are seeking then by all means post your question. There are many friendly and informed members here only too willing to help you.
We also have our own App - It is a very simple app to navigate.
http://itunes.apple.com/us/app/discussion-forum-for-ipad/id412896524?mt=8
Reading the IPad manual is a great place to start so please download a copy of these.
http://www.support.apple.com/manuals/ipad/
2 very informative threads from which you will learn many tips and shortcuts for the IPad.
http://www.ipadforums.net/ipad-general-discussions/21590-tips-tricks-those-us-who-dont-know.html
http://www.ipadforums.net/ipad-os/49581-ios5-tips-tricks.html
We have rules like any Community so please read these also
http://www.ipadforums.net/forum-rul...um-rules-everybody-please-read.html#post14697
Once again we welcome you here and are so pleased you have joined us!
