Go for the ETS EC.
Either the
ETS EC 125/3 (as it uniquely takes both sizes 125/150 of pad) or the
ETS EC 150/5 (for the slightly quicker stock removal)
I have the Rotex 125, ETS EC 125/3, RTS 400, Mirka Deros 5mm. And have twice bought and sold the Rotex 150 for specific jobs.
The Rotex is awesome in rotex mode for fast work & material removal, with excellent precision and dust extraction over something like a belt sander or grinder. A sheet of 80g paper on the rotex will remove material as quickly or faster than my Mirka Deros 5mm with 40g paper.
The 150 is a far smoother handling and better balanced machine of the two rotex sanders.
And finally the normal radom orbit mode of the Rotex 125 is terrible, on so many levels I can't be bothered to go into it. I don't remember if that's similar to the 150, I suspect the 150 is better in this mode, like most aspects between the two, but probably still not class leading. You buy the Rotex for Rotex mode.
The ETS EC is fabulous. I purchased the 125/3 as it can uniquely accept both the 125mm and 150mm pads. It might be the nicest, smoothest sander out there and I love it.
In 3 years of owning both ETS EC 3mm and the Mirka Deros 5mm I have gone back and forth on which sander I prefer using day to day. The Mirka does remove material slightly quicker with the 5mm stroke, but it's not really noticeable in most day to day cases. I find the Festool a little more refined in use as well, less likely to bump an adjacent surface, or tear out splinters when softening the corner edge of a board. The Dust extraction on the Festool is noticeably better than the Mirka although the Mirka isn't bad at all.
The ETS 125 (the non-EC kind) is probably not the sander to get! It is for fine finishing, not for taking 2mm of the edge of a cabinet door in a pinch, or sanding a rough sawn board to smooth and flat.
Anyone asking themselves if they want/need the Rotex, will defiantly be unhappy if they choose the ETS 125

Any box store sander costing £80 is a faster and more aggressive sander.
The Mirka Deros is a fine choice too. The GOOD things are that it's smaller, lighter, more manoeuvrable, and the 125mm pad has holes for literally every type of 125mm paper I've ever come across. Also this sander performs great with full power extraction, so if you have a non adjustable Vac/DC setup, you'll definitely prefer it. The festools notiably prefer a reduced suction to run smoothly on a flat surface.
The BAD is the reliability seems to be an issue if you look at/trust the internet, although mine has been fine for 3 years. The velcro pads wear out 3x faster than the festool IMO. The paddle is occasionally annoying and rarely much of a benefit. Dust collection is worse than all my festool sanders. Not in a room filling way or anything, simply more dust on the work bench and sander itself after extended periods of sanding.
Currently the ETS EC is my favourite sander to use day to day, but 18 months ago I would have said the Mirka

I'm a fickle human

Both are fabulous.