Honestly, I can't see Sidious taking a victory over both right away unless he goes for a Force Storm out of the gate, but I don't know how long he needs to gather such a powerful attack, anything short of an immediate attack is conceding the momentum to the team.
Remember that Krayt has tanked very strong powers himself and Kun's already formidable defenses are reinforced with an amulet, one of which Lucien Draay tanked a bombardment with. Anything less than a Force Storm is not beating that kind of defense quickly.
No, Draay's was from a random Kressh family member IIRC, meanwhile Kun's is the more powerful, Focus of Naga Sadow. Not like Kun's amulet hasn't performed defensively itself, easily absorbing the sorcery attack of Aleema Keto and then blasting her in the face with it.
Again Kun and Krayt can't win if Sidious takes the offensive first, but he isn't beating them down combined either.
The properties of all amulets are similar even though they are somewhat varied, Ulic's own amulet protected him from a Basilisk Wardroid's main armament, Kun's amulet seemed to absorb lethal levels of disintegrating dark side energy and then channelled it back to knock Keto out with it. Elcho Kressh's guantlet was simply geared more towards protection.
Basic properties, perhaps. But the Gauntlet of Kressh the Younger was expressly designed to absorb anything that might threaten the wielder. Kun's gauntlet was designed to amplify the wielders rage, its offensively orientated.
Both were constructed by powerful Sith sorcerors, so I don't think it wise to assume that Kun's gauntlet has at all as good, let alone superior defensive capabilities cause reasons.