Either way you will end up with a great reg. The question here really becomes do you want to dive a vintage reg or do you want to dive a double hose reg, there is a difference. The Phoenix is for all practical purposes a modern reg, it just uses some vintage parts and vintage designed parts in it's construction. It has modern internal parts and all the functionality of any modern reg, the later Mistral that AL released a few years ago is a direct comparison, same internals as a matter of fact. You can choose to dive the Phoenix in the vintage style or as close to it as you choose (Octo or none, LP inflator or none, SPG or use banjo or J valve) or you can equip it fully modern if you like or need to. The reverse is not completely true of the DA or most other DH regs, if you want/need a SPG you must use a banjo or other means, if you want an octo or LP inflator it is possible to do using the hooka port (DAAM and RAM- not the Mistral and other DH regs). From a parts and servicability standpoint they are close to being on par with the Phoenix being a little ahead because all of it's intenals are standard AL parts that fit the Titan, Conshelf and almost every other USD/AL reg from the last 40 years. You will likely have to learn to service either of them yourself because most shops will not touch a DH reg. Any good tech familure with USD/AL regs should be able to service one, just convincing them to do so is the problem. You can always upgrade the DA/RAM to a Phoenix later if cost is an issue.
I own several of each. From a diving perspective there is little difference between them although the Phoenix and RAMs can be tuned a little closer to the edge that the others. Which I grab depends on the day and where I am going. For travel, I take the Phoenix just in case I run into the scuba police. No police and it has a SPG and maybe an octo.