My gut feeling is that anything grouped, whether it's categories or items on sale, is always better as it's easier for the viewer to digest the information presented.
If you're considering replacing products displayed on the homepage with simply links to categories, I wouldn't recommend it. People shop visually and it's more inviting to show products, whether grouped or featured, than simple category links.
With that said, this is the perfect opportunity for an A/B test. Take some cues from large ecom sites like Amazon and Newegg and see what they do as well.