Hand engraved is the best. Machine engraved is the worst---and I don't know beans from apple butter about laser engraved---except for my knee-jerk reaction that it sounds a lot like "machine".
Now when I say the best, I'm talking about value---value as respects the cost to buy one---and value as respects sustained value. Hand engraved values are highly influenced by the artist--the better the reputation the higher the value---and very likely the rate the value appreciates. The value of work by a master is better than money in the bank!
That's a short course from one who's not even remotely qualified to present it. You want to be talking to Richard Garner (RKMesa hereabouts). He has, in the vernacular, Been There, and Done That! He has what is very likely the premier collection of EXTREMELY high quality engraved guns of anybody here. My best guess would be Bill Cross (Doc 44) runs a close second, but that's because I've seen what I suppose is a lot more of Garner's guns than I have Cross's. All of either's I've seen will knock your socks off---art work of the first rank!!
Ralph Tremaine
As an aside, I suspect "level of engraved" refers to the percentage of the surface area engraved. "Full coverage" translates to every place it has a place. That said, I've seen different levels of full coverage. Most recently, one of Garner's was FULL coverage---leaving no room for anything additional. Lest one suppose that might be regarded as gaudy, this one was anything but. S&W factory engraving was (and perhaps still is) labeled as A-B-C; A being full coverage. As to what's the most attractive, that's in the eye of the beholder. Again, one of Garner's recently shown was downright sparse when it comes to the area covered, but it was so tastefully done, it was enormously attractive.