That separate title is the key distinction, and it is what makes a semi-detached home different from a duplex. Each half is owned and financed independently, so a buyer of one side is not exposed to what the owner of the other side does with their unit. Minimum down payment rules apply the same way to either type, 5 percent up to $500,000 and 10 percent above that.
Practically, the difference shows up in noise, privacy and resale pool. A semi-detached buyer accepts a shared wall and a smaller lot in exchange for a lower price point than a detached home nearby, which tends to appeal most to a first-time buyer or a downsizer.
Which one fits depends on what a specific buyer is trying to trade off, price against privacy, not on which type is objectively better. Get your hand-reviewed valuation from Joel Dyck.