I don't get what would be different from port forwarding normally and with UPnP, it's the same thing except in one case you're doing it yourself, and in the other you're letting your router doing it.
If it really was that similar, then both would be showing the ping instead of "---".
So it is not.
Port Forwarding is basically telling your router where to send packets if it is in a port range and the router doesn't know where to send it.
UPnP has to keep broadcasting things like device services and information over an entire network every time a new device is added or when a player tries joins the server.
In a big network, it slows it down significantly and poses
huge security risks as malware can use it too.
Also, not all devices support UPnP.
I am not as familiar with UPnP as I am with Port Forwarding, but I do know
some players are unable to join UPnP servers.
For more information, please refer to
Wikipedia
