Our best midfield is Onana alongside Garner I think. They complement eachother well and are both very accomplished on the ball, which I like. We always have a chance of controlled retention of possession with them in the side, which makes a big difference to our tempo.
Gueye is alright like, but has a tendency to vacate his position to go in search of the press which often leaves us open, and he is much less controlled on the ball. Perhaps Gueye is a better option when we are trying to win the ball high, but Onana gives us more time in control of the game.