You can compare the UK range
here. Remember all the photos are of US models. The models ending in 5 are UK models and have the 4 coloured buttons.
The latest model is the ONE which is a worldwide model and does NOT have the coloured buttons. Arguments/Views rage on that ONE!
It appears that the ONE in all other respects seems to be the best laid out ergonomically etc. I have the 555 and its great other than keys size layout etc.
The good news is that basically the software is the same across the range. Models mainly vary by, with or without RF and screen variatiions etc.
Be prepared to alter your way of thinking when you buy a Harmony, think ACTIVITY (what you want to do) as opposed to DEVICE (what you want to do it to!)
Good Luck
Alan
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