I've tested 3 attenuator:
Bugera PS 1 at ¤79
Jettenuator at ¤128
SPL Reducer at ¤369
The SPL and Jettanuator use fancy aluminium housed resistors, the Bugera has plain ceramic resistor that sit elevator from the pcb for cooling.
All 3 devices have just resistors inside, I was expecting some additional components in SPL to justify the price, but only the housing is nicer, the electronics are not.
The SPL has a noisy and cracking potentiometer, the other 2 are noiseless when adjusting the damping level.
The Bugera has an extra feature in the dail that consists of a magnet, a metal plate and an unknown wired component. I'm not sure what this is for, but I think it's to stabilize the resistance of the potentiometer. The more expensive Jettenuator has the same potentiometer but without these extra components.
I didn't have the SPL available for a side by side test, so I only tested the Bugera and the Jettenuator side by side. They sound almost exactly the same, the Bugera is slightly smoother and the Jettanuator sounds slightly more brittle. To me, the Bugera is the more realisticly sounding device.
On both you lose some depth in the sound. Although I find the sound surprisingly good.
Even if all were the same price, the Bugera would be a clear winner for me. The SPL is very disappointing at that price level.