He is better than Denis at CM
Denis is too chaotic as a CM
I have the same problem with Denis for now (I know that it is way too early).
He has Rafinha's vibe of being all over the place, or playing as a 4th attacker at times, and then when we lose a ball on his part of a pitch there is an insanely giant hole and our first players to tackle a counterattacking opponent are a fullback and Busi.
I don't know how to describe it in words in a better way.
Rakitic and Gomes cover similar area. When they have to attack, they can attack. When our team loses a ball, they are in the right place to recover loose balls.
Iniesta plays closer to attackers, but he is not lost when we lose the ball, he is positionally on a right place to recover loose balls and to stop counterattacks.
Rafinha/Denis play differently. Kinda of too attacking/too close to attackers/too close to an opponent's box.
At times our formation from the air looks like a 424 then. Our midfield (Busi-Raki-Rafinha/Denis) seems "empty" then, and there is that thing with counters and loose balls in that 424 formation where we have only Busi-Raki and a giant hole on an area where Rafinha/Denis play (as if we play with 10 men).
Or in a defense, Rafinha/Denis often play like this (1st goal from Alaves):
https://www.youtube.com/watch?v=KgohIQjhijA
Opponents run past them as if they don't exist at all.
Denis/Rafinha maybe have better skills/shinier tricks but Rakitic/Gomes bring way more balance to a whole team, imo.
They cover much larger area both in attack, and especially in defense (in recovering balls).
(Again, I know that it is way too early, but Gomes has a lot of potential, it seems)