This is a comparison of the same league in both v13 and v14 after a 31 year sim.
This league was created in v13. I cleared out all team/player history in the league and then imported it in v14. I made no other changes to either league.
OOTP13 Year to Year Summary
OOTP14 Year to Year Summary
OOTP13 Season & Career Batting leaders
OOTP14 Season & Career Batting leaders
OOTP13 Season & Career Pitching leaders
OOTP14 Season & Career Pitching leaders
What I seem to see is that initially offensive output was higher in v14 than it was in v13 and pitching ERA was higher in v14 compared to v13. But then they converged when I hit about year 21/22 of the sim. The v14 numbers seemed to come back into line with the v13 numbers.
This seems to indicate that the v14 PCMs produced better pitching/poorer hitting. Early on in the v14 league the stats were produced by players created in v13. But as more players who were created in v14 made it to the majors the league batting stats lowered and the pitching stats improved.
Here are graphs representing League BAVG and ERA over the 33 years.