I'm having difficulty determining if one rank vs another of my pet's or spells that create pets (Blighted Horde and Awaken Grave), are stronger or weaker than other ranks. Is Awaken Grave VI (Apprentice) stronger than Grave V (Adept)? Is Grim Sorc VII (Apprentice) stronger than Grim Sorc VI (Adept)?
typically, you want to move up to the highest tier of the spell. Unless it is master/grandmaster vs apprentice, it will most likely be better.
In order from weakest => strongest Apprentice > Journeyman > Adept > Expert > Master > Grandmaster > Ancient