I'm going to go in order of the GCs from the selection menu to make it simple.
The Stars Align:
-Imperial Remnant: Easiest
-New Republic: Hard
-Pentastar Alignment: Easy-Normal
Fractured Empire:
-Imperial Remnant: Easiest
-New Republic: Hard
-Pentastar Alignment: Easy
The Hunt for Zsinj:
-Imperial Remnant: Easy
-New Republic: Normal-Hard
Thrawn Campaign:
-Imperial Remnant: Easy-Normal depending on how many Katana Dreadnaught you could get. (Because if you could get 27 like I did once... Let's just say it's a big boost.)
-New Republic: Easy-Normal depending on how many Katana Dreadnaught you could get.
Empires at War:
-Imperial Remnant: Easiest
-Pentastar Alignment: Easy
-Empire of the Hand: Normal
-Duskhan League: Hard (I know they are not playable, but I hope they will become playable too in 2.2 so I decided to add them into this one too)
Into the Cluster:
-Imperial Remnant: Easiest
-New Republic: Hard
Shadow Hand:
-Imperial Remnant: Easiest
-New Republic: Hard
This comes from the fact that IR has Ardus Kaine and Palpatine + the Sovereigns which can oneshot Wedge and the Lusankya which is a great problem. If you could find a way to limit the superlasers' maximum fire duration under the point where it destroys a SSD(or viscount) then it could be much more balanced and more challenging to the IR players... though it would lose some difficulty from the NR's POW
-Imperial Remnant: Easy
-New Republic: Normal
Reunification:
-Imperial Remnant: Hard
-New Republic: Easy-Normal
Black Fleet Crysis.
-New Republic: Normal
-Duskhan League: Easy
Final Imperial Push:
-Imperial Remnant: Normal
-New Republic: Normal
-Empire of the Hand: Normal
I think this is the most balanced GC in the whole game in my opinion. I could say that EotH has a slight disadvantage because they have no SSD, but the Phalanxes and the strong bombers and fighters balance it out, so it is perfect. I play this GC the second most.
Essence of War:
-Imperial Remnant: Easy
-New Republic: Normal-Hard
-Pentastar Alignment: Normal
-Empire of the Hand: Normal
Imperial Civil War:
-Imperial Remnant: Easiest
-New Republic: Normal
-Pentastar Alignment: Easy-Normal
This is the top spot in my book. Played this GC the most... What can I say? I love large GCs.
Art of War:
-Imperial Remnant: Easiest
-New Republic: Normal
-Pentastar Alignment: Easy
-Empire of the Hand: Normal
From the Ground Up:
-Imperial Remnant: Hardest
-New Republic: Hardest
-Pentastar Alignment: Hard
-Empire of the Hand: Hardest
As I noticed the PA version is MUCH easier than the others because they start in a region with good income and when Dathomir is taken there is nothing what can stop PA from taking the CSA and gaining lucrehulks and getting more good income planets.
Corey, we need a harder one for the PA
You have to ask someone else about the balance in survival though... I remember trying once with the Remnants, but lost interest. It's not my thing.
I hope this will suffice.