The reason your only getting the item delivered to one device and not both is that Tigase, unlike Google Chat, is following the XEP and delivering the message to the connection with the lowest priority (or to the device that logged in last if the priority is the same.)
You need to be careful when trying to bind your JID to a specific resource and look to make sure the resource you requested was actually assigned. The server may not give it to you because it conflicts with an existing JID's defined resource.
Google Chat servers do something "special" in that they deliver the message to any connected JID regardless of resource or priority setting. There are some changes being suggested to allow that behaviour by design but those have not yet been accepted by the XSF yet.
If you want delivery of messages to all connected devices I would suggest that you look into creating a PubSub node on your Tigase server and set the node to deliver to any online JID - then all of your devices will receive any message that you push to the node if they are online.