whether you should buy a bar of milk chocolate or a bar of plain. Both of them are chocolate, but they taste a bit different - it depends on your personal preference.
The Apple is a lovely machine - looks nice, and does exactly what it says on the tin. You can run Microsoft Office on it, and to all intents and purposes it will be just like any other laptop, except it's a Mac. That means that an awful lot of commonly-used software won't run on it, and that may be a deciding factor, particularly for your daughter.
Using your brother's Mac software isn't allowed - it's a contravention of the licence agreement, so don't try it.
The Toshiba might be a better bet, simply because your daughter will be at university with people who will almost certainly be using Windows laptops, and any file-swapping will be that much easier. She'll also appreciate the larger screen for those long evenings spent poring over Excel spreadsheets (at least, that's what she'll tell you she's doing).
In your shoes I would go for the Toshiba.