Yeah, I'd see detection as the biggest determinant too. But if directed energy weapons are the choice you have the interesting situation where they don't necessarily do catastrophic damage instantaneously, and you're providing a giant beacon to return fire at, so I wouldn't discount defence entirely. Maybe even a simple reactive defence of explosively launched optical chaff, deployed fast enough, could buy a fraction of a second to return fire and turm an engagement into a mutual loss or a millisecond game of system targeting precision/luck.

Which is where missiles could potentially have a place. Assuming you have the detection initiative you could dumb launch one or many without necessarily giving away your position, then allow them to drift far away from yourself before igniting to mask your location.bThey would be incredibly vulnerable to directed energy weapon interception, but depending on the technical capabilities of the weapons, them firing on the missile(s) might provide the safe window to disable then with a directed energy weapon of your own without suffering immediate return fire.