I spent some time this afternoon comparing all of the latest
@MrWalkman firmwares on my 1A and 1Z. For the IEM I used my Campfire Solaris 2020 with AZLA SednaEarfit XELASTEC tips and a DHC Clone Silver balanced cable.
Luckily I have two Sony WM1A players and was able to compare Project Z (Plus) on one 1A directly against another 1A running DMP-WM1 FE (Plus) and my 1Z.
So here is the configurations tested:
WM1Z running DMP-WM1 FE (Plus)
WM1A running Project Z (Plus)
WM1A running DMP-WM1 FE (Plus)
Here are the tracks I used for testing:
Helplessly Hoping - Crosby, Stills and Nash - Crosby, Stills and Nash (24/96)
Cathedral - CSN - Crosby, Stills and Nash (24/96)
Landslide - Fleetwood Mac (Remastered) - Fleetwood Mac (24/96)
World Turning - Fleetwood Mac (Remastered) - Fleetwood Mac (24/96)
Don't Give Up - So - Peter Gabriel (DSD)
American Idiot - American Idiot - Green Day (24/192)
California - Blue - Joni Mitchel (24/192)
The Patient - Lateralus - Tool (24/96)
Invincible - Fear Inoculum - Tool (24/96)
The tracks were chosen for multiple reasons. Vocals, instruments used and mastering.
The 1A running Project Z (Plus) has a deeper fuller sound over the WM1A running DMP-WM1 FE (Plus). It also has a wider more 3D soundstage along with improved details. I can understand why some people might prefer DMP-WM1 FE (Plus) over Project Z (Plus) if they have either a bass heavy IEM and/or not using an OCC silver cable. In either case, DMP-WM1 FE (Plus) is a huge improvement over the stock Sony firmware, but I prefer Project Z (Plus) over it.
I then compared my WM1Z running DMP-WM1 FE (Plus) to the WM1A running Project Z (Plus). The WM1Z running DMP-WM1 FE (Plus) has the deepest fullest low end with the smoothest details and a larger more 3D soundstage. The NW-WM1A Project Z (Plus) comes close but not as full or smooth. This is most likely due to the differences in hardware.
So to me with the IEM configuration I tested, the overall winner was the 1Z running DMP-WM1 FE (Plus).