Well, I wouldn't say its a noobie question, and I'm actually surprised I havent seen it before!! Minions are usually for use at the beginning of the game only for schools that aren't Myth, because later on, Minions are easily killed in battle. Minions also tend to have lower rank spells that consist of blades, traps, and 4 pip and below spells. Henchman are available in all schools, and at different ranks (and prices) and have higher rank spells, health and skills, making them better for higher worlds, and tough bosses.
In Other Words, Minions Are For Low Levels, Henchmen For Tougher Things
Hope This Helps
Julia DragonLeaf-Level 87 Ice
Megan DragonLeaf-Level 26 Storm
"The Best Things In Life Are Free, But Wizard101 Begs To Differ!"
Well, minions are just spells you use to call that particular creature to do your bidding. A henchman can range from 20 to 90 level and have a higher range of spells than minions will ever have. I stopped using my minions on all my wizards after Dragonspyre because my spells I was gaining were more powerful than what my minion has. I use henchmen only for the level 58 spell quest and to battle Mithraya in Trial of Spheres. Henchmen are not incredibly expensive but if you use them enough you can find your crowns going down quite well sooner or later so use them sparingly and only if you really need them. Only problem with minions is that after a boss exceeds level 8 the minions are not very effective allies.
Minnions are for free, Henchem are more powerful depending on there level, there both pretty good. Myths get stonger ones than other minnions and death's minnons health and rank depends on the player's pips. Though I don't like to use both of them sometimes, besides the healing henchmens, because they use up me traps.
Any minion that gets stronger the more pips you pay to it are worth using beyond Celestia or Marleybone. Fire minion is pretty useless, as an example. If they allowed leveling up of minions or at least upgrading, that might change, but alas, there's no word on that as of yet