Like Kosty stated, adaptive isn’t always guaranteed to be up. It has the most uptime on a bubble gunship, but I rarely run either ship with bubbles (mostly I use ions). Most of the times when I fly an empire gunship, I am not moving around nearly enough for the adaptive to have even 25% uptime, which takes away its usefulness. I would put the shield slot to use for a compact shield for extra energy, or a volume increase if I’m using particle purge.
2 cpu slots can easily outweigh 2 cap slots, it depends on how you use them. DE has a crit chance increase as a passive bonus, while Achilles does not. More chance of crit = more damage output overall, so the 10% crit chance bonus basically acts as a 3rd CPU slot.
Sure, the Achilles has a 15 resistance point increase for hull and shield, but shields on an empire ship don’t mean all that much, and 15 points for the hull isn’t even half of a galvenized. You would have to guarantee 80%+ uptime for an adaptive to make the Achilles more tanky than the DE, but that additional tank is immediately lost upon dropping afterburners or being slowed by a tackler.