They are more commonly referred to as "bump" cabins. They are not any larger than the others since if you look at the deck plans you'll see the whole cabin is moved outward since the passageway curves too.
This is just my opinion, but we had a cabin on the smaller bump on the Freedom - it has two bumps - and I didn't think the view was any better than from the other cabins. I do think the cabins on the forward part of the bump are more susceptible to wind. Personally I wouldn't waste a lot of time trying to get a bump cabin.
I don't know about the RCI ships, but on two of Princess' ships (Island Princess and Coral Princess) there are some privacy issues with the cabins right at the "bump". On several decks the first (or last) cabin on the bump looks right into the balcony of the cabin just before the bump. This might be something to consider. And the field of view of the cabins on the bump is only a few degrees wider than the others--as Dave says, nothing to spend a lot of time trying to get.