I think you should choose solid
Because ore is the best choice for mining.
Why??
My and my friend's experience are examle.
We always lost about 10-50 peds for per mining trip.Also,we were very hard to get global.
When we change the material to mine (chose ore).We never lost more than 10ped because the markup is so hight.In addition,we often got global about 5 global for 10-15 mining trips.