Both boxes are running Android 9.0 Pie with the new BuzzTV 4.0 Update.
Key difference between the 4000s and 4500s is the S905X3 processor as opposed to the S905X2 in the 4000s, along with GIGABIT LAN!! (finally!)
XRS model has increased storage capacity from 32 GB to 64 GB.
The timeline for release is between now and end of February.
Specs for XRS4500 (High End):
Amlogic S905X3
4GB DDR4 RAM
64GB Storage
Dual Band WiFi AC
2X2 MIMO technology
Gigabit LAN
Optical
Bluetooth Remote with new Backlit Buttons
Buzztv 4.0 Integrated IPTV Platform
Specs for XR4500:
Amlogic S905X3
2GB DDR4 RAM
16GB Storage
Dual Band WiFi AC
2X2 MIMO technology
Gigabit LAN
Optical
Bluetooth Remote with new Backlit Buttons
Buzztv 4.0 Integrated IPTV Platform
I hope these boxes are running an arm64-v8 (64-bit) variant of Android as opposed to the armv7 (32-bit). These processors are more than capable of running a 64-bit OS.