Hi

I just finished the game with the other 4 candidates. For me these guys are the best:
Alchemist--> Barbatos.He makes free boost potions (after you fetch him the book) and for the second platdorm upgrade he requires an amulet so you can drink the potion of wisdom yourself which Allan wants :P Does anybody know what his brew does anyway?? + for Allan's quest rewards you get only 1 skill book.
Trainer----> Hermosa. For the second platform upgrade she requires a sword not the book Demon Wars (or something). And if you read the book yourself you get 5 skill points! Like with Allan you get one skill book as a relard at best if you choose Kenneth.
Blacksmith-> Wesson. He has 2 platform upgrades ( for some reason Radcliff has only one) and you get skill books from each of his quests :P
Necromancer-> Didn't find any real difference :| but I prefer Joneloth. Becoming a master to a guy who poisons his former master (and abandend his first master) doesn't sound like a good idea to me xD