I have a Kindle DX and a regular Kindle. Love them to death.
The regular Kindle is great because you can hold it in one hand and read. it's very light.
The DX is much heavier. It's like a hard cover text book.
No one holds a large hardcover in one hand this way.
The best way ive' found to read the DX comfortably (of course there's plenty of ways to read hardcovers. These are not new

) is to use a folio case which makes it open like a book so you can hold it like a book. You can get very good balance this way ,just like a hardcover.
The iPad is no different. I wouldn't try to hold it naked for more than a minute (I'm weak ) as the balance is poor.
But i will read it all day long with a cover just like the DX, which is comparable in weight.
Owning the DX has been a asset regarding this, as i've already thought it though; mostly with trial and error (I bought a lot of cases)
your move.
note: I prefer the DX by far, regardless of the weight, and never use the smaller one.