I've now spent a fair bit of time looking over the three "hack" documents I have, "Redbox Hack," "Old School Hack" and "Dino-Pirates of Ninja Island: Old School Hack Version." Curiously, I've found that all of them have things that I prefer to the other two, but none of them alone really completely "does it" quite right for me.
"Dino-pirates Hack" is the closest, but that doesn't completely work either. Here's a few comments on what I like and don't like about each version. Or more honestly, in many cases, it's not about what I like or don't like as much as it is about what works for DARK•HERITAGE and what doesn't.
Old School Hack is an ENnie Award winning game, and the first one that I heard of and read. It's certainly got the best presentation, the best layout, and the tools near the end to facilitate a graphical representation of the arenas and whatnot is really pretty cool. Curiously, it's also a much better emulation of "Red Box" D&D than Redbox Hack. Of course, that's also part of where I have problems with it. It's too D&D. I don't really like Elf and Dwarf or Goblin as character classes.
I'm also not convinced on the Awesome Point economy and the way it's set up. I know that it's worked in plenty of playtests, but I don't know that it's been playtested as a campaign vehicle as opposed to a one-shot or shorter game vehicle. I can also imagine the incentives that it's supposed to engender, but I tend to find those kinds of incentives built right into the games that blatantly come across as kind of corny and gimmicky. I can imagine leveling up happening way too fast for my taste as well, based on the Awesome point economy the way it's structured. I prefer Redbox Hack's more traditional "XP" system to a big bowl full of Awesome points that anyone at the table can give to anyone else, and which they have every reason to as often as they can..
Also, I have a dislike of landscape format documents and character sheets. I don't know why they seem to be more popular these days in pdf format. I'm a traditionalist there too, I guess, in preferring portrait style layout.
Speaking of which, Redbox Hack eschews fancier layout for clearer text, in my opinion. I had an easier time following the thread of how the game works in that document. Despite the shortness of all the documents, I still find my eyes glaze over reading mechanics these days, so that was appreciated. Kirin's layout on OSH occasionally had me wondering what part of the page I was supposed to go to next, and I felt like just following along with the text was occasionally difficult, because it bounced all over in little boxes and columns and non-traditional page layout that made it a bit hard to follow. Although it looked really Spartan in comparison, the RBH organization was a lot easier for me.
The implied setting is a bit weird however; anthropomorphic animals being a character class isn't something that I'd likely get behind. I also thought the attributes in OSH made a bit more sense to me than those in RBH for whatever reason.
Dino-pirates Hack (not its real name) was the one that was closest to what I'm looking for right out of the box. However, it really wasn't meant to stand alone, and well... it doesn't. The one-page summary of the rules is nice as a reference, but you couldn't possibly understand how to play just from reading that.
The classes were a lot more likely to be useful to me, although I'd still need to customize them a bit for DARK•HERITAGE before using them. I also really liked the sample adventuring goals page, which was a nice little addition--not necessary, but quite helpful.
So my hybrid DARK•HERITAGE Hack will feature attributes from OSH, classes mostly from DPH, and advancement and the Awesome point economy mostly from RBH. I'll add a few tweaks to all of those, especially with regards to advancement. I also want to inject a bit of roleplaying elements into a game that's not necessarily designed to focus on them--I want to include a Sanity trait, and have a Sanity mechanic that harks back to the classic Cthulhu mechanic of the same name.
I also want to include a small bestiary and a few other tools as part of the game up front; none of the three has that, although there is an online supplementary bestiary for OSH that I could use as a starting point.