The z400 is the first samsung qchat phone,not sure about the other.

Both the LG LX400 and the Samsung Z400 will be the first of many more High Performance Push To Talk/HPPTT CDMA handsets powered by Qualcomm's QChat via Sprint's CDMA EVDO Rev A network allowing HPPTT customers to use Nextel Direct Connect/NDC to other HPPTT customers as well as Nextel ones. The LG LX400 will be an entry level model where as the Samsung Z400 will be a mid grade one.

Blackberry Curve w/ HPPTT (QChat) is coming... 🤤

The next Nextel Blackberry will be straight iDEN 🤤