The chemical Methyl Ionone exists in many forms, called Isomers. They all have similar properties and similar (although slightly different) smells. The percentages mentioned, refer to the amount of each isomer (alpha methyl ionone, beta methyl ionone etc.). The number at the end of a descriptor (e.g. Isoraldeine 70) refers to the amount of the major isomer in that material. The name Isoraldeine refers to the Methyl Ionones made by Givaudan, as opposed to Methl Ionone made by another company. As is often the case, small amounts of other chemicals (impurities, if you like) can make a large difference tothe overall smell. The method of manufacture will produce slightly different amounts of these trace elements, and different amounts of each isomer, resulting in different smelling materials.
Deciding which one to use, is up to you. They all smell slightly different. All Methyl Ionones have a powdery, woody floral, violet smell; but each types is slightly different. Some are more Violet, some more woody etc.