DRS gives you registered ownership without a paper certificate. The transfer agent holds the position in your name, sends you statements, and pays dividends directly. Because the shares are not in a broker's nominee account, they cannot be lent, pledged, or caught in a broker failure.
The costs are practical. Selling usually means instructing the transfer agent or moving shares back into street-name-registration first, which takes days and can be expensive. Options, margin, and fast execution are unavailable while the shares sit in DRS.
DRS became a retail talking point during meme-stock episodes as a way to remove shares from the lending pool. Whether it materially affects a float is contested; what is not contested is that it changes your legal position from beneficial owner to registered holder.
Related: street-name-registration, dtcc, rehypothecation, locate-requirement