I’m not really a regular ‘high polish’ finish guy so I’m not the best to comment. But as an owner of the RO125 and ETS EC125 I can safely say that if you buy the ETS EC your rotex will see a LOT less use.
The ETS EC does not compare to the RO when it comes to large material removal, but it’s not bad at it, and unless your looking to remove actual mm from a surface, it will likely be almost as quick while INFINITELY nicer to use.
I briefly owned the ETS 125 (one of two Festools I ever returned) and while I’ve no doubt it will finish an already smooth and flat surface brilliantly, I wasn’t interested in a tool with such limited scope. Hoping it might be more of a general 125mm sander, I was disappointed by its weakness. Literally every other 125 orbital I have ever used is notably more powerful.
But if we’re talking swirl marks under a microscope then many here have high praise for the ETS 125.
Personally I think the ETS EC 125 (that wasn’t available when I first purchased the ETS I returned) is a fantastic finish sander, and it can do higher rates of removal too.
The ETS EC 125 is my favourite festool sander, but I’ll never sell the RO125 cos when you need it you need it.
My actual favourite and most used sander is my Deros:
Lighter, smaller, as or more powerful and takes all types of paper (in terms of hole patterns).
But I have the 5mm. The other option is 2.5mm stroke. That’s right between the 3mm of the ETS EC and the 2mm of the ETS.
Finally, be aware that there seems to be a bad batch of the ETS EC around at the moment, as after 5+ years in the market, with plenty of rave reviews, there have been several posts here lately about brand new sanders failing.