The iPhone version has three major differences that make it nowhere near as good as the version on the 360: 1) Downloadable Content (DLC); 2) Multi-player; and 3) screen size.
The third problem is completely excusable - the iPhone has a small screen. Even the DS version suffered from this to a degree, though it was offset somewhat by having two screen to work with. But with the iPhone, it got tedious: zoom in, zoom out, scroll - zoom in, zoom out, scroll - wash, rinse, repeat. And the Technology Tree, that was a real pain to work with.
The iPad version should be a real treat. Much more like the 360 or PS3 versions. You'll be able to see a lot more of the world at once and with more detail. Less scrolling and zooming. I hope. This IS all based off descriptions and screenshots. The iPad isn't actually out for a couple of days so I have no way to play it hands on.....yet. :)
But, again from the description, failings 1 and 2 are not corrected in the new version. Nowhere is a mention of multi-player capability or DLC. Those are deal breakers for me. And the reasons why I still play Civ Rev on the 360 but never fire it up on my iPhone.