When we first bought the 2019 version of the Cube I noticed how much faster it was in terms of general use. You soon get used to that to. But it is nice. It seemed faster than the old Firestick and even faster than the 4k version. It also has 16GB of storage.
The 8GB of the Firestick works out around 5GB to use.
WiFi wise it is only the new Max version of the Firestick that supports WiFi 6, but still 8GB of storage.
I have read an odd post or two that suggest a new Cube could be out soon.
The 2019 Cube and the new Max use OS ver 7 rather than 6 found on the std 4k stick, iirc.
We tried the Cube on WiFi, very close to our main Asus RT AX88U router, and it seems better when we used a Gigabit ethernet dongle fitted. But that is limited by the USB 2 port on the Cube.
The new MAX supports WiFi 6 if your wireless network at home does.