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That article mentions couple of things about the Lynx.
> equipped with active, passive, and reactive systems to protect against rocket-propelled grenades and anti-tank guided missiles.
> The Lynx is also armed with the next-generation Lance 2.0 turret and the new Wotan 35 electrically-driven cannon
I assume these are the things that are "better" than the Redback. The lighter weight can come from the thinner armour, less capable weapons, less ammo (or same amount of smaller rounds)... I dunno, Wotan 35 as the name says 35mm autocannon, but Wikipee says K21 has a 40mm one.
I'm not sure about the armour protection, even tanks can be taken out with relative ease, so a heavier Lynx with thicker skin might not be that advantageous.