I still think they should have given cactus armor a small thorns set bonus instead of extra defence.
Beetle is just all around better. The passives from both chest plates are good. Sure, turtle has the 100% thorns bonus, but when you are in hardmode you don't WANT to receive damage on purpose.
But thats the point, I want to receive damage, hence why I have the Paladin's Shield. Out of my friends, I am the tank, I'm supposed to take boat loads of damage, I have two buddies who does mage, one focusing on healing prowess and the other on DPS. We also have a ranged guy, and then one of my other buddies is also a tank, but he is built to deal damage.
We're playing hardmode Expert right now and so far it hasn't been an issue when facing bosses, but I'm still torn.