The main disadvantage of the Centurion is that it is slow and needs the crit or some other boost to MAT to truely shine (all other heavies but the hammersmith are 7's or 8's). Conversely the advantage it has is the high armor for more survivability and the polarity shield to help secure a cygnar charge hits first.
Lets see which of our casters take fix his disadvantages and capitalize on his advantages! (this will be long)
Stryker: The addition of another Arcane shield means you can afford to put one on your cent. Armor 24 is crazy high, and on feat turn Armor 29? Also earthquake can insure he hits without needing a crit so he can buy more attacks.
eStryker: Positive charge makes him MAT 8 POW 20. Warjack bond gives him a potential 4 dice to hit on his first attack. Crit sustain anyone? Also his reach gives him a really great threat with eStrykers feat.
Haley: Ok, so TB makes polarity shield useless. But -2 Def and the second Arcane shield make him a force to be reckoned with. Also the blitz attack takes advantage of the crit sustain for an auto hit.
eHaley: Telekinesis and Temporal Acceleration. Nuff said.
Caine / eCaine: OK so niether really helps out the cent... But he probably wasnt gonna take a heavy jack anyway.
Nemo: 5 focus and locomotion with disruption field anyone?
eNemo: need I even get into it? You can have a whole front line of no charging, not to mention energizer for speed, and fail safe for super survivability. Oh, and the feat turn.
Darius: He's darius, the cent is a jack.
Siege: No much here, so probably wont make it in over that defender.
Kraye: Full tilt gives an 8" move then shield, or an 11" threat charge with reach on the feat turn, not to mention he counts as heavy Cav and has a higher STR then most of our other heavies for impact attacks.
So, of 11 casters, 3 do not have some way of either overcoming the cents low speed or boosting its survivability. Many of the bonus's that our casters give may work on all of our jacks, but the centurion gets better effect from some bonus's then others.
Being able to get 4 dice on the first attack for a crit against high defense casters with eStryker is a prime example.
Does this mean its the best jack out there? no, but it does it mean it will still certainly see the table and continue to be put into lists? most definitely.
But to finally answer the OP's question, yes. The higher defense in hordes gives greater value to the Centurions crit sustain, its Higher armor benefits it because of hordes general lower power, and the polarity shield helps prevent those extremely maneuverable and fast beasts from hitting your line first.