You're probably not going to get any solid answers from that question, quadman.
For one, every builder has their own idea of what an "HRD" or play duner porting will be...one might decide that mid range and ok top end is where the power needs to be, one might think that high end is where the power needs to be on a dune port, with little emphasis on low and mid.
Some builders can't make an all-purpose port that lets you ride trails and hit the dunes without major deficiencies, some can.

If you want specific differences in how they run and what type of work is done to them, that's on a builder specific case.
If everyone did the same work, there wouldn't be a question of which builder was better, it would be a question of which is cheaper and has better customer service.
You'll have to ask each builder what their differences are, and odds are you won't get the technical answer you want because they're not going to divulge every aspect of the work.
They'll tell you how the engine will run, but they won't email you a port map of their cylinder.
Timing the ports to X degrees, triple porting the exhaust, opening the intake up more, raising compression, going to the last bore size, etc., is not everyone's recipe for an HRD.
Some builders might not even call it an HRD, or even offer something similar to that performance.
Granted, there's a few things that most every builder does to get more power, but they're rarely interchangeable in every scenario.
You can't go to X builder and get the intake ported, then go to Y builder and get the exhaust ported and expect them to run well together.
What you want to know is who can build an engine that does what YOU want it to do, unless you're wanting to compare porting from a specific builder.

Grkguy is a great example of why you can't ask a question like this and expect an unbiased answer.
He was being helpful, but he just couldn't help dropping the name of his favorite builder.