I didn't see any difference, as expected the gain is very little that we don't even realize it. My main trainer was 5 lv. and youth trainer was 4 lv.
Player 1: 6 RB, 6 JS, 6 HA, 6 DR (13 1on1 G and 1 RB training -18yo-, 4 1on1 G, 10 RB training -19yo-)
Player 2: 6 RB, 6 JS, 7 HA, 6 DR (13 1on1 G -18yo-, 4 1on1 G, 10 RB training -19yo-)