I suspect I know the answer, but I’ll ask.
I have half a dozen Hue dimmable bulbs. I do not use a Hue (brand) hub. But I did get a more current Amazon Echo which supports Hue bulbs.
I suspect that the Hue bulbs are “proprietary” and you must have a hub in order to use them, unlike a lot of current bulbs which are open Wi-Fi or Zigbee? If so, they will be out soon. I’m headed as much as possible to an open system.
If so, which is “better” for dimmable bulbs? Zigbee? Or Wi-Fi?
Hue communicates over Zigbee and for that it needs a coordinator, currently that’s your Echo. I can’t tell if the echo is able to expose the bulbs to openHAB, if not you need to switch to another coordinator.
You can use a zigbee stick, generic zigbee-bridge or the Hue-bridge for this, the latter can be used locally without cloud.
Personally I like the HUE lights and these integrate well over the bridge, but they work just as well using an alternative like zigbee2mqtt or the openHAB zigbee binding.
I use them mainly for accent or mood-lighting, main lights are zwave operated dimmers with normal warm-white dimmable led-bulbs.
Cool. I have a sonoff coordinator
With the echo control binding you can expose devices connected to your echo to openhab.
Therefor it should be fine to connect hue bulbs to an echo or any other ZigBee hub. Only some non standard features like music sync and maybe firmware update will not work
Matthias,
That would indeed work for me (for now).
BK,
I have WiFi devices (2 LED lights) that are controlled BOTH by Echo and OH which is maybe a slight plus (and probably a recipie for disaster. 
). I know if I reteach the Hue Bulbs to OH, then Alexa would have to control via OH. Which is FINE with me as well.
Some great input. Thanks guys.