I suppose if you want to think of it terms of one over benefiting the other, then that would be one reason.
Most of us just like to have added features to our consoles, and allow ppl like our kids to be able to access them without getting onto our pc.
Never really thought in terms of one being better or having more benefit, just something that is available to use, if you want to.
Here is what to do: Install them to your pc and play some games. Then install some to the wii console and play some games.
After your done, you can make an assessment of which has more benefit over the other. That is if you really want to.