Depends what you use the pi server for. Plex? Shield is much better. NAS? Kinda works but not flawless in my experience. Torrenting? Possible. Automatically downloading via sickbeard/couch potato/sonarr/radarr and the likes, not possible. Installing all kinds of other Linux packages, not possible
Why use it as a plex server when Kodi or VLC shouldn't break a sweat reading files off an external hard drive.
I find that Raspberry Pi running OpenELEC or LibreELEC (Dedicated Kodi on a bare bones Linux) will easily share out a hard drive for streaming over the network. However Android devices running Kodi cant share out a hard drive and need an SMB client installed.
I dunno about the torrent part but it's a great Plex server.