DLNA is media file streaming.

It's 'similar' to just having your files on your desktop and opening it on your client device thru a file sharing protocol (ftp/smb/nfs/etc). There will be buffering lags, the decoding is done by the end device* (may have codec issues), and DLNA end points are not as ubiquitous as HDMI ports.

*Ok, the server may do some transcoding too, depending on the implementation.