Personally I think playing centurions as "broadsides" wastes their potential, they have relentless and limited range, walk em up in the battle line as a support unit to kill targets that threaten your other units. With grav amps and their huricane/ML setup centrurions are a danger to every target on the field be it light infantry, heavy infantry, MC's or vehicles. even better than oblits they aren't forced to premeditate each turn what target they want to engage next turn and act accordingly. They have no invul sure but with readily available cover that is not as much of an issue, furthermore their lack of powerfists is not a major drawback as they don't need to win or die in combat due to ATSKNF, not to mention oblits should never be in combat.
as to the assualt version, those are straight up better than mutilators in almost everyway, they have good delivery options that muti's can't get, they have a higher base T and better weapon loadout, they have special weapons to engage the enemy before charging, they aren't locked into alternating between good CC weapons and Bad CC weapons like oblits, and they strike at I with their stupid siege weapons.
edlargal, hmm yes I would say that wraithlords can fill a similar roll in the eldar army to obliterators, thats not a bad thing. The wraithlord however is vastly different in terms of stats, wargear, and rules. whereas centurions really do seem to me to basically be imperial oblits/mutis, right down to their size and wound bracket.