Hi Robert, welcome to the forums
I'm not sure how much of a difference this would really make. However. if you downsample the image before sharpening you're more likely to introduce sharpening artefacts. The greater the resolution of the image the more latitutde you have for sharpening before you start to oversharpen.
Personally I wouldn't downsample and then sharpen unless I really had to. You've got less pixel data to sharpen and so to get the same sharpening effect you're going to have to sharpen more (I think
)!