It's obviously something that Democrats in NC have stumbled upon recently (as we fell out of redistricting power for the first time in many decades - and felt the resultant pain)... but a completely impartial redistricting scheme tends to favor Republicans.
This is because Democrats are far more likely to live in super-majority clusters that dilute our electoral influence.
Take as a hypothetical example an inner city (population 100) that's heavily minority and votes 80-90% (we'll say 85%) for Democrats... surrounded by three suburbs (100 pop each) that are 55-45 Republican (largely white). How should district lines be drawn? The total population of the area is 220 Democrats and 180 Republicans... but the only way we avoid a 3-1 representative split against us is to draw districts with little fingers into the city center. You could even draw four Democratic districts (each largely suburban but with enough downtown population to give us the majority). But that's not the way that an impartial panel would draw the lines.
I propose that the power to create voting districts be taken away from whatever partisan faction is in control and that voting districts be created by a "jury" of citizens tasked with creating political voting districts with only raw population data, no voter registration information, to work with.
It sounds fair... but it would ruin us. There isn't an impartial jury in the world that would take my example above and do anything but draw a nice pretty circle around the downtown area and split the suburbs into three reasonably comfortable R seats.