I have a few of the stone molds and they work fine. As far as +/- here are a few thoughts:
+ = cheaper than alum molds, many are made outside US, so you can find replica bait molds that may not be otherwise available
- = the molds used to take about 6 wks to get once ordered. However some are made in Ukraine, which may be hard or impossible to deliver currently. They need to be oiled before use to prevent sticking, stone could break, the ones I have are all one cavity.
CNC Alum - baits will be professional looking, molds are solid as long as taken care of, they are costly, depending upon the bait can be found in multiple cavities. There are numerous bait companies to look through.
6" swim bait - I would look at the open pour molds at Angling AI.
6+" not sure.
Hope it helps.