What is the difference between the available suppository bases?

Suppocire AS2X is a suppository mass with additives. The main one is Tween. Where one would expect a Span to form a W/O emulsion. Possibly the manufacturer fears that this would compromise the absorption.

Novata B has a rather low melting point of 33.5 °C and a short solidification range; good for suspension suppositories

Witepsol H 15 has a low hydroxyl number between 5 and 15; required for drugs such as paracetamol, salicylic acid, diclofenac, indomethacin