Two very different styles of play. I ran the Dread on one of my tacs for a while and had some fun in eSTF play. Depends on your playstyle. The Dread is a beast once you learn to fly her. But she is definitely an acquired taste. If you are used to flying Fed Whaleboats, you will have an easier adjustment.
Since you mentioned preferring escorts and if you haven't got one already, I would advice looking into the Mobius or Krenn temporal destroyer. It has a nice turnrate and has, in my opinion, a very nice bridge officer lay-out. I'm running with plasma weapons at the moment and because the ship has 4 tac slots and 4 science slots, I'm able to use 4 tac consoles + 4 -threat science consoles which lets this ship dish out some serious damage. Thanks to the BO lay-out you can still make this ship durable even without resistance or shield based consoles.
On choosing between the escort carrier and the dreadnought, I can only tell you what I think of the dreadnought as I haven't flown the escort carrier yet. The dreadnought turns like a whale but it's a beast and a beauty.
It's very durable on my tac captain so it should be even more so on your engineer. The damage it can put out is pretty impressive as well. I guess if you have the ability to use elite scorpion fighters, there's no downside to the dreadnought as far as I'm concerned.
My experiences come from mostly doing STF's, fleet and romulan events, so if those pve missions are your cup of tea you really can't go wrong with any of these ships. The price difference might be the biggest factor here as the escort carrier is around 60 mil with the dreadnought and destroyer being in the 80+ mil range last time I checked.
I have the J'HEC on my Engineer. I love the look of it, prior to it's release I actually ran the holo-emitter of it on few ships. Equipped with the MACO set, I tank an Elite Tac Cube for quite a while between the J'HEC's large number of Eng BOff spots (for an escort), solid hull, and my capt abilities. The turnrate is more on par with a Sci ship at 13, but far more than enough for PvE DHC usage. The single hangar is a nice goody, which I have loaded up with Elite Scorpions.
I really like the console that comes with it. The team buff to damage and get out of holds Fleet Maneuver Gamma gives is great, especially if you PuG a STF and end up with a team that's just a bit low on damage. I like it better than what I've seen of the J'Dread's console, with it being random as to what system can be knocked off-line. The two-piece set looks cooler when Fleet Maneuver Gamma is fired off, and the defense buff I'm sure is handy in some situations.
The only issue is thematic. I switched to Polaron and was intending to grab the Mk XII Jem set, until I tried the Mk XI Jem Deflector and Engines with Mk XII MACO shields and nearly got rolled at the opener cube and spheres of ISE... For survivability I need a Positron or MACO deflector, without it I end up with 48,751 hull instead of 51,522. Not sure if the Jem Mk XII shields would be capacitive enough to be worthwhile for the two-piece bonus when going with a Positron deflector.