Fine... I will bench it myself
Simple test is to see how fast thumbnail cache can be done on 165k files
Local SSD 39min
NAS WD3tb Red 2h11min @gigabit speed
The cpu was at 45%ish when building thumbnail cache off the SSD. (I could hear the cpu fan spinning up a bunch)
The cpu was at 12% when building off the NAS WD3tb drive. It was only at 2.6Mhz of the 3.2Mhz. (Fan was silent)
This was all a no brainer I guess.
As far as the speed when adding new music, they are about the same. The album is added rather quickly to the MC server. (SSD or NAS) Press F5 and wait less then a minute and the music will appear on the server. The SSD is quicker like 30s compared to 60s. (not a deal breaker for a NAS) Anyway I'm guessing the audio is only analyzed only so often when set to auto. The waveform eventually shows up, unless I force it manually. (Less then a hour on NAS or SSD). As far as the speed of it showing up on the client, I find it is easier to just restart the client and the new albums will show up. (SSD and NAS are the same speed)
So in conclusion, an SSD is faster at thumbnail creation. duh! Once it is created then there is no benefit to putting the actual mp3s on a SSD. I'm sure a SSD in a NAS would be much faster then a mechanical HD in a NAS. The point is a SSD is not going to speed anything up except the initial library scan. Unless I connect 10000s clients an SSD is not needed. The MC server Library is on a NVMe, that is all the speed it needs. My client computer is so fast anyway I can't tell any difference between a NAS and SSD. Once the library is loaded, then only thing that speeds up the server is CPU and NIC speed.