Originally Posted by tanin

I have almost the same dilemma and was close to getting the Cabin Plus (in addition to Cabin and Compact), but as for now, I suspended the idea.
For me, there are two key aspects:
1) The possibility of taking it onboard - if it will not be checked by agents. When flying in economy without proper status level, they may classify it as over the limit. And sometimes also weight may be an issue. The overhead bins should be OK, but the limits are not. So there may be a significant risk. But, if you fly business all the time, this may not be the issue for you.
2) Additional space - like do I really need it? OK, it is significantly bigger than Cabin, but most of my trips are rather short ones, so Cabin is enough, even during the winter. And when I go for a longer time, I usually prefer to do some shopping there, so due to liquid restrictions (and weight) I prefer to have checked luggage.
Original Cabin is slightly bigger inside than the Classic, but the Classic is a sort of icon of the design. So, if you need every liter of capacity, go for Original, but if you prefer the design, then Classic should be your choice.