I have only discussed the relative defensive capabilities of the two classes. Avengers were chosen because they are arguably the most offensive of Paladins.
I can talk about that if you want.
Offensively, APs have dual wield and third attack. They also have bloodlust for haste/regen/AOE attacks. They can drop iceballs to suck away your mvs, lag you out with trip/bash/weapon controls. They can deafen you. They can worldbind you. They can energy drain your mana/mvs away. They can sleep you, spell you up, and cripple you with physical debuffs, and instakill you with cleave. APs have infinitely scaling unholy weapons which allow them to snowball hard.
APs are infinitely better at offense than Paladins. To imply otherwise is frankly rather stupid.
The most offensive Paladins (2H/monk) lag themselves out HARD (strikes/intensify) to deal less damage than iceball spam while dual wielding and bloodlusting.
Even when a Paladin is going full offense, they do not represent anywhere near the level of threat that APs do, and still do not have the level of damage reduction that an AP is able to easily achieve using wands and scrolls.