Get a quote to rebuild a high horsepower turbo charged and after cooled diesel and then go get a quote to rebuild a 120 lehman or 135 perkins naturally aspirated and you will see a huge huge difference. As well, see what the average/typical life is for a high HP diesel with turbos and aftercooler and how many hours you can hope to get on an engine like that vs/ a low horsepower, naturally aspirated engine.
There is a reason boat manufacturers with a true displacement hull stick to low hp, naturally aspirated diesels. And yes- I agree 110%- most "trawlers" are only fancy marketing words for hulls that are planing hulls with "traditional" looking cabins built atop them. Owning both though, I expect the life of my perkins 135hp naturally aspirated diesel will be longer than the (still relatively low hp) 220hp turbo diesels in my 45.
Yes, I agree, big hp diesels at hull speed will burn near the same as low hp. Turbos don't like that long term though and they will definitely burn a little more than their low hp/NA cousins but hull speed is hull speed. A full keel with protected prop is not the same as a hard chine hull with very little keel and exposed props. So...a Carver 440 is no more a trawler than my bayliner 4550 is but they both can get darn near trawler economy but both lack the efficiency of a single screw, low hp/NA diesel with full keel and large fuel tanks for their size vessel. My perkins burns around 1.5 to 1.75GPH, my 45 at hull speed burns reportedly around 4-5GPH with both engines running. My 45 has soft chines and prop pockets, my Monk has hard chines and full keel. With her soft chines, low center of gravity, good tankage for her size, keel that is just a hair lower than the lowermost point of the props, and great fuel economy at hull speed, one could argue my 45 is a trawler but she isn't...she's a pilothouse.
But...nothing beats a full displacement hull with low hp diesel, naturally aspirated engine, full keel, protected prop, low center of gravity, and large tankage. There are few full displacement boats out there coastal cruising though due to their deeper draft.
One of the more interesting marketing terms I saw on a boat ad last week was a new phrase for me. They labeled it a "Pocket Mega Yacht." haha. Loved it!

Let's not pretend a large aft cabin high HP motor yacht or a pilothouse also with some turbo diesels are trawlers. At the same time, how does grand banks get away with calling their 25 knot boats "trawlers." LOL. Gotta love marketing. We are a generation that want their cake and eat it too...trawler with some speed.
BUT- back to the original poster...we went from cruiser to trawler and loved it. There is something undeniably appealing to cruising slow in a boat with beautiful classic lines that turns heads everywhere they go and does not look like every other boat out there. As well, never having to worry about fuel prices is a great feeling. And teak. Who cannot love a boat with beautiful teak inside and out. There is a calling for that type of boat IMO and it can't be replicated by a more modern boat. The nights we spent anchored out on our Monk 36 with some quiet jazz or classical playing on the radio in her rich teak interior as we sat and talked around the salon table around the oil lantern are among the best times I've ever had on the water and memories I would not trade for anything.
Maybe it is more about a love for classics than anything else?