The two Edges have different names, so their effects do not stack
In Savage Worlds Deluxe, the Edge is Martial Artist. In Deadlands Reloaded, the Edge is called Martial Arts.
Thus the only benefits you get for the Martial Arts Edge in Deadlands Reloaded is as follows:
You’ve trained in martial arts or boxing, or learned to street fight really dirty. Your character’s body is a finely honed weapon, so even when your hero fights unarmed, he is considered armed. In addition, opponents in melee combat never benefit from any gang up bonus against your hero.
I'd like to point out that "opponents in melee combat never benefit from any gang up bonus against your hero" is extremely powerful, and no setting after Deadlands Reloaded has repeated this.
Why have two Edges with similar names? Deadlands Reloaded was created while Savage Worlds: Explorers Edition was the latest version of the core rules. That version lacked most of the Edges related to unarmed combat. The Martial Arts Edge was introduced in Savage Worlds Deluxe, which was released after Deadlands Reloaded.
The SWD Martial Artist Edge is not permitted in Deadlands Reloaded
When Savage Worlds Deluxe was released, Pinnacle released "Deadlands Deluxe-ified", a PDF explaining how to incorporate the changes from the new core rules into Deadlands Reloaded. That document explicitly states that the Martial Artist Edge for Savage Worlds Deluxe is not available in Deadlands Reloaded (emphasis mine):
The following Edges are not allowed in Deadlands Reloaded: Arcane Background (Psionics) or (Super Powers), Martial Artist (or any Edge that lists it as a Requirement), Mentalist, Soul Drain, and Wizard. As usual, characters may only take one Arcane Background Edge.
Regarding your other questions
In Deadlands when it says “considered armed”, is that the +d4?
No, this refers to the Unarmed Defender rule (page 76 of Savage Worlds Deluxe). Since you are "considered armed", you are not subject to the effects of the Unarmed Defender rule.
Or in this case is there a version where you ignore gang ups or get +d4 to punches?
There is no version of the Martial Arts Edge in Deadlands Reloaded that allows you to get an additional d4 for punches. The closest thing is the Deadlands Reloaded Edge Superior Kung-Fu: Eagle Claw Style, but that requires Arcane Background (Chi Mastery).