I was just creating a new suit for my level V8 DK and I put on the enchantments I made (purple) and was comparing them to the armor that had lower level potency enchantments on them (level 6 armor). They are the exact same stats. Both add 520 stamina for instance. One is a level 6 piece of armor using a level 7 potency (Derado) for level 5-7 armor. Since this new armor is level v8, I have to use level 8 potency to add the enchantment to the armor using Rekura. There is no difference in strength in either glyph. The only thing different is the names, grand verses splendid, and the level of items you can apply it to... if you are advancing a glyph to higher level potency glyph, the enchantment strength (potency) should be higher, duh!