Melo's highs was higher then Marchisio's last season, but also defenitely hit lower range with his performances (mainly the brainfarts with losing possession or temper). Overall had slightly better season then Marchisio (because his good performances were commanding, vital to our midfield), but to the point it didnt matter because of Melo's inconsistencies and the difference between them being mediocre to slightly less mediocre.
Marchisio last season, and in general last 2 seasons is a player who is consistently held the similar level, generally underwhelming and bit average one, but never really hit anything close to rock bottom with his poor performances (thats more noticeable, thats where the childish ghosts came from, you dont notice him doing mistakes, just another player going through the motions), just almost allways the similar type of mediocre performances. Kinda "reliable" in that way. But also at the same time his highest ceiling was bit low, when it came to the better performances (remember the Genoa game, and the Milan game when he hounded Ronaldinho like hell, but generally otherwise similar "reliable" performances of underwhelmingly ok). Quite a stark difference to this season.
Besides growing as a player and with boosted confidence that comes from having a coach's trust, he has allways been I player I dont see fit into in 4-4-2 (most coaches prolly semi-realized that, hence trying him as winger etc), or more specifically two man CM pairing. All the way from Azzurrini to now, found his best dynamic showing in a 3 man midfield that offers more freedom and less responsbilities for him (thats why it was extra dissapointing for me, saw every Azzurrini game he played basically, clearly saw the promise, only for them to lack the edge in most of his Juve games, that were in 4-4-2 formations). So extra good for him Conte found this working formula, think his season (the teams) would looked quite different if we continued with 4-4-2.