Yeah, there's no comparison really. Highgrove products are high quality, have a genuine royal link if that's something you care about, and the proceeds go to charity. Also, if you visit a royal site you can buy the products there and then, and in other outlets too.
Whereas Meghan's products are basic white labelled items, no different from anything you can buy for much less in any supermarket. You also have to pay delivery costs and wait for them to turn up. People aren't going to buy them just because she had a photo taken with members of a foreign royal family. They already know she's a Duchess, and that seems to be her only selling point.