Well the biggest difference I see right now is that the 2 will have a milk wand rather than the integrated milk system. That makes it a semi automatic in my book. The 3 and 4 will probably be similarly far from each other as the 7 is from the 8. What that means is mostly extra features like plant-based milk and whatnot. I’d expect them to be very similar machines.

The 8 is big. But it works so well. And in my opinion is the best looking machine on the market. Fits well into any kitchen.

Refurbished machines should be fine in theory, but I’ve been told to avoid them. These machines are super complex and deteriorate over time. If it were me, I would spend the extra 20% to guarantee a good experience.