Answer to the OP question: Defender is better. Unless you're Altar or custom faction with that henchmen trait or have earth spellbook tier 5 (giant form + diamond skin). Only with this, i can consider warrior equal to defender, perhaps better. I will only highlight the henchmen, because the earth spells are self explanatory.
The advantage of this henchmen is you can give mini spellbook to the henchmen. If you create a warrior henchmen with Life and Fire Adept then Bloodthirsty, or just fire adept and bloodthirsty and give life adept to other henchmen that will always stick close to the warrior. You can boost this champion atk status by 100% by doing that, meaning doubling its attack. Now just take the +atk bonus in warrior trait, plus that 100% boost, using a weapon with 10 attack can give you around 50 attack against injured enemy (10 from weapon +15 total from traits, multiply it by 2), if this is combined with warrior weapon specific damage bonus trait, it will boost it further by 75% to 88 damage, not counting crushing blow, which will boost it even further.
The good thing is you can achieve this at just level 9 or 10. And altar henchmen doesn't split experience like normal champion does, this combined with relias starting air spellbook which have tulelage on it means this kind of situation is easily achievable in no time, add the quest map too for fun. Too bad the unique weapon for altar is a sword, you need weapon other than sword to do this. I often do this, in practice it's good enough even for ridiculous/ridiculous map setting with largest map size and 9 AI opponent. If you have a spear that has at least 15 atk, this warrior can do 100 damage to enemy units with impale.
Also worth mentioning is growth spell can stack if it's from different henchmen, not champion but henchmen with life adept. It's most certainly a bug, but idk for sure.
You can create a good combination by creating that warrior, pair it with henchmen mage with life adept and commander that has battle cry (usually i make my relias as commander). If you want all champion army, try 3 warrior, 3 mage (mostly for buffing) and 3 commander that constantly spam battle cry and watch the fun. Only doable with altar or henchmen trait because of the exp split.