Nah I love my advent but the destra is a very expensive and difficult ship to bring to a fight. Typically you won't have researched plasma upgrades at all until after you start pumping out destras, and at the point you can get destras, it is only another temple or two before you can start doing armor increase research. Do that instead and your illums are nearly as good armor wise as base level destras, plus you already likely have laser research high and that helps both your bombers and your illums. If money was no factor and you could afford the upgrades, the destra becomes a decent ship..HOWEVER.
As I discovered against a well informed opponent, the destra only has heavy armor and it shoots a composite that "only" does full damage to light frigates. Cobalts are cheap, costing nearly half the value of the destra each and they can be pumped out very quickly. A swarm of cobalts with upgraded armor can outlast and kill a much more costly fleet of destras. The obvious answer is a mixed fleet.. which means you're back to throwing money all over the tech tree again to get everything upgraded. Illums only with a push for armor upgrades seems to me a better option. Another thing.. destras have a horrible turning speed.
Ah another point though.. against the marza barrage, destras have a much longer lifespan than illums. Something to think about.. better to push the damn marza with guardians and use bombers (with laser upgrades) to take out the marzas I suppose.