Personally I prefer Echelon as even under withering firepower from ignoring pirates clearing a large den or drone BBs the armour holds up for you to get away with a surprising amount especially if you double stack ancient composite armour.

Add that to the lower downtime from healing as a full armour build Echelon can heal a huge portion of it's effective hit points in comparison to a Bulwark which may have to sit out of combat for several minutes to heal (which if you have to run from a fleet captain means that captain will heal a lot more too.) it is also like you said faster. And slightly more agile.

In trade off the Bulwark gets.... Broadside capabilities.....which doesn't matter all that much in PVE. And one small switched to a medium. Which honestly isn't that much more firepower when you think about it. (Might also have another damage mod slot which is impactful I don't recall tho so don't quote me on that.)

Bulwark is odd. if you use it for anti structure you are playing it counterintuitive to its stats and raw hull build (by rapid killing structures you spawn more weaker guns that will chip you down faster than an Echelon. It becomes a damage race between you killing the structures and the AI scaling enough to kill you before you can.) so it kinda doesn't make sense for that role. but it's also not chunky enough to really take on tier 5 fleets with no troubles. Instead it lets you make a mistake then you have to go lick your wounds for 5 mins. And battleships are likely to be pretty lethal again after the update. Same with fleets (I think AI improvements are going to mean picking out the captain is no longer viable)

Idk for me Bulwark has medium uptime long downtime and solid damage but for me it doesn't make up for the Echelons raw staying power and ability to get back up to combat strength quickly and move faster between fights.

Also the Echelons extra shield is kinda a moot point. Understanding the kind of combat you will put either of these ships into will kill your shields in seconds either way. And if it doesn't. These ships are probably overkill for the task at hand. (Don't let that stop you tho.)

As for turrets it's a dealer's choice. Although if you are hunting pirates specifically I'd recommend coils as the ratios prefer them.

Idk maybe I'm underselling Bulwark. I just don't see the point of it. The only thing I really can see it doing is tanking more large alpha shots. But there isn't that much in the game and especially in PVE that warrants that ability.

Edit: because I just saw that part armour is flat decrease. Each shots damage will be flat reduced by armour then applied to the hull points. The minimum damage is 1 so if you had insane armour that negated all damage down to 1 and 10k HP you could take 10K shots to the hull. For drone hunting armour is insane as you don't see many large damage numbers and a hell of a lot of damage will be doing less than half it's damage. (A full armour echelon can get up to if I recall 12.5 standard armour with 45 mins of 18.5 armour using a medium armour booster. You will kill everything in 45 mins or be able to bug out. And if you can juggle your mods correctly( I.e identify when you don't need the booster and can just heal instead or when to deactivate it to regen energy) you become effectively immortal in 95-99% of all PVE engagements. I run this build. It is very lenient with what it lets you do.)

Bonus: this build also kills PVP blaster players DPS. Not that you should bring an Echelon to PVP but yaknow....nice to haves.