I really suggest the MacBook if you want to do email or post to a forum., etc.
An iPad can be a little cumbersome when you are being charged for every minute you are connected. It is better to be able to download your email, read it offline and then reconnect to send your replies.
You can type offline and send online as well as download emails on line and read off line on an Ipad. I do it and just did yesterday and for the last two weeks on Mariner of the Seas
NAVIGATOR OF THE SEAS - 7/6/14
NAVIGATOR OF THE SEAS - 9/14/14
NAVIGATOR OF THE SEAS - 9/21/14
OASIS OF THE SEAS - 10/14/14
NAVIGATOR OF THE SEAS - 11/4/15
NAVIGATOR OF THE SEAS - 1/11/15