Impossible to say, really.
Believe it or not but iPhoto 11 uses the same database engine as Aperture 3, so it should be equally robust. It is certainly true that there are a lot less of the "Oh No iPhoto Lost All My Photos!!!!!!!!!!!!!!" type posts on this forum - and a lot less exclamation marks too - but then it's reasonable to infer that many of the users here are more experienced users than on the iPhoto forum. That may account for the difference.
Aperture is a much more powerful app than iPhoto and there is a learning curve. The opportunities for organising are more varied and flexible, but also more complex. It's much much better with Referenced Libraries.
Aperture is geared to the Pro shooter who shoots high volumes and probably Raw. If you're shooting Jpeg and low volume it may be overkill. If you're a serious hobbyist it definitely has value. If you're taking snaps of the kid's birthday party to send to GrandMa it may be overkill. So it really depends on the kind of photographer that you are.
The best thing to do is to download the free trial -
http://www.apple.com/aperture/
import a few hunderd images and explore. The tutorials here
http://www.apple.com/findouthow/photos/aperture.html
are well worth a look too.
Regardless of which you choose you will always need a good back up - or several...
Regards
TD