Hello There,
IMO BlackiesHotDogs's point needs to be considered...
I've used all the three schedulers mentioned, so "it depends":
PowerGold is a strict, statistically good performing tool: if you know the rules and count the values (sep times, points, etc) it works well. On the other hand you always need to refine your rules and database/categories to get most out of it. However because of this you can control - almost - everything; if you want.
MusicMaster is an artistic approach: with the Optimized Rules you don't need to refine the system if you add the 8th Madonna song to the same category, it handles virtually everything - if you want/set accordingly.
The data/automation import/export works better on MM, I daresay.
You can ask for trial with demo database as far as I know however it won't tell you much I'm afraid.
If you'd like to add any "extra" fields to the MM database (Year for eg) you need to phone home to apply the changes... I've never understood this.
If you're running a CHR/TOP40/HOTAC station maybe MM would be a better option due to constant changes - I'm using that for those stations. For AC/SoftAC (lot of songs, no tight rotations) I'm running PG. No Selector any more...
Best,
SIR