If you (or your wife) are enthusiastic about photograhy and are willing to invest into a steep learning curve, then Aperture is the tool that will give you the most satisfaction.
iPhoto you can use without ever reading the manual. For each task there is only one way to do it, and it is quite obvious how to do it. In Aperture there are several ways to do it, and you have to configure Aperture before you can use it. You could compare iPhoto to a Swiss army knife - just one tool for each purpose - and Aperture 3 in comparison is a well stocked workroom with lots of special purpose machines, and you have to set up these machines, insert the correct bit into your drill etc., and you need to learn how to do it, the first year you will feel like a craftsman's apprentice.
I used iPhoto for about a year, and was quite happy with it, but then I began to notice the shortcomings of a swiss army knife and was longing for a proper work bench.
The biggest drawback of iPhoto is the storage requirement. If you edit a picture, iPhoto will store two image files, the original and the edited version. Aperture will store the original master image, but if you edit an image, it wil only store directives how to produce the version and a preview of the version. If your library grows, you will appreciate this difference. While I was still using iPhoto, I always had to fall back on iPhoto diet, to remove unwanted copies. In Aperture you can browse your library, even if the master files are stored on an external drive that is not connected.
And if you are travelling a lot and shoot in different time zones, you will appreciate the much clearer handling of time zones and camera time, and the better handling of GPS data.
In iPhoto you have no control over the file names, in Aperture you have.
And if you invested into a decent camera and want to shoot in RAW to get the most out of your images, then you definitely should use Aperture (or Light room).
So just ask yourself - are you (speaking about photography) happy with a swiss army knife or are you passionate do-it-yourselfers in need of a well stocked workroom and willing to learn - test it by reading the Aperture 3 User manual
Regards
Léonie