4 defence dice with an evade token and possibly AT evades is.
4 Dice with an Evade token can fail and does quite often. Even if you only put 2 damage on him, he's that much closer to dead on the next attack. Plus then he only has 3 dice for that next attack.
AT on the other hand, offers very little other than against turret weapons, which are fairly common but are not the only thing in the game. For a number of lists you'll see AT upgrades being nothing more but free points for the other person.
