ARMER is simulcast (unless you're out in the boonies).
Scanners don't tend to handle simulcasting on P25 very well. Unicast P25 audio is generally decoded pretty well by most scanners, so WISCOM is just going to sound better.
Colorado's DTRS is 800 MHz w/o (much) simulcasting and they sound great. ARMER and SC21 usually sound bad, really just tolerable most of the time. Of course, the gear that the users use is better so they don't hear it as poorly as scanner users will.
VHF helps too - but it's not the whole story.
Good point, I have heard before that simulcast impacts scanners. I wonder if VHF scanner listeners on the Washington county system notice a difference between that simulcast county system and WISCOM sites?
Simulcasting is nice from the governance side as you don't have to fight as hard to get frequencies since all sites share. On the other hand its more expensive to add capacity since a channel upgrade needs to go on all sites in the simulcast.
My experience also shows 800 provides better in building penetration. Simulcast seems to be better too since you are getting penetration in a building from multiple angles.