In my most humble opinion, CIM clear is the best. BUT...if you plan to use any of the silver reactive glasses or silver foil...even gold and in some cases, dichro, copper mesh, any type of inclusions basically, use only the CIM Clear...not the Unique Clear. That one will crack your inclusion beads in a heart beat.
Also, besides cleaning with alcohol, use KIM Wipes...like for your eyeglasses to dry them off. Even paper towels can add scratches to the clear glass. Would you wipe your $400 eyeglasses with paper towels or Kleenex??? Not me anyway...
Always burn off the first glob off the end of your rod since you will always get bubbles/scum where a rod has been cut. Work with a little less propane/a little more oxy...that too will help.
And...as easy as it might be to use 1-2mm stringers for encasing, larger rods actually will give you less scratches...causing more bubbles/scum. I hardly ever have to peel my clear rods anymore...
I encase 99.999% of my beads and all these tips and tricks I have learned over the years plus the new CIM clear make life so much easier.
Good luck.
Sue