Where I live, we have a Midwest League affiliate; my observation over the years would be that the league tends to be more on the pitcher friendly side.
The South Atlantic League (Greenville) and the Midwest League (Fort Wayne) are considered equivalent level minor leagie (Low-A).
Looking at Baseball Reference, historically, the SAL and the MWL have been pretty similar in offensive numbers. This year, the SAL was slightly better offensively:
MWL .249/.317/.335/.672 with teams averageing 4.05 runs per game
SAL .250/.319/.372/.691 with teams averaging 4.20 runs per game
I wouldn't read anything into Espinosa's performance at either place. He's 18, 3.5 years younger than the average player in those leagues. This trade really can't be evaluated for at least 3 and probably 4 or 5 years.