I think it depends on your system size and your requirements. I don't think it's really any different than it has been, except more people are falling for snazzy marketing around prop-based powerheads. They're really great in the right system, for sure. But in other systems, with other goals, closed loops make a lot more sense IME.
On my 360g, I had a closed loop with a pump that had a 1/2 hp three phase motor and a variable frequency drive that was run from an arduino-based controller. I got all the controllability of a contollable prop pump, but the power, reliability, and clean install of a closed loop. It was effectively invisible, versus the many gigantic ugly slotted black eggshaped powerheads I would have needed to get the same power. Even on half speed, it basically made that 4' x 6' tank look like it was boiling. It was dead reliable and rebuildable with industrial-quality components that were designed to operate for years in harsh environments, and there was real customer service available for all of the components, not a hobby-grade help line. If I was going to do another system like that, I would do the same style of closed loop, without question.
Meanwhile, the nano I just set up has a Jebao prop pump on the back wall where it can be kinda-hidden by the overflow. It works great and I really appreciate the simplicity and control. If the pump dies, no big deal. If I need to pull it and clean it once in a while, no big deal. If I did another nano, I would use the same approach, without question.
I get the point of this thread and marketing materials have really promoted the great features in prop pumps these days, but IMHO that doesn't really change anything. Even 10 or 15 years ago, you could choose between a closed loop or a controllable prop pump (Tunze), and closed loops weren't obsolete then. I don't see how they would be now. The prop pumps are cheaper and available from a wider range of vendors but really, not much else has changed.
