Ummmm...not necessarily. Having the extra height along the length of the knife is very handy for transferring food from point A to point B. And the rounded nose is a nice place to rest your hand if you want to rock chop--which some santokus do just fine. The length and balance feel very nice on mine--some of the big gyutos make me feel like a freaking fiddler crab. Is a santoku the end-all, be-all knife for every situation in the ultimate scheme of things? Well, no. But neither is the gyuto. Like any other knife, it depends on what's comfortable and what's important to you as the person using it. I have both gyutos and santokus and like them both. Luckily I don't have to settle for a just one kind of knife.
ar11, if you live anywhere near a knife store, I'd advise going there with your wife and handling some things and see what she likes and is comfortable with. What you like, are comfortable with, and is something you can maintain in a manner that keeps you happy is what's important. And if you decide later you want something different, sell the one you don't like and get another.
Here's a comparison of some tips. At least one of them is a santoku. At least one is a gyuto.
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