Arsenal should hold territory and push Fleetwood's wing backs deep. Fleetwood's back three can meet the first cross, then use a direct ball or restart to reach its forwards. The size of Arsenal's advantage will depend on clean first contacts in both penalty areas.
Fleetwood's home cup defence has repeatedly reached those first clearances, and Coughlan, Evans and McLean give it cross and second-ball outlets. Arsenal can still create through Eze, Madueke, Dowman and Rice, even with Saka and Saliba ruled out after missing Everton; its recent heavy-possession games also show that entries do not always produce many accurate first shots. Fleetwood's McCann played its last league match but is suspended for this cup tie, so the outlet work shifts to the remaining wing and forward group.
Arsenal can press from the opening exchanges, while Fleetwood can stay compact and seek relief through a forward release or set play. The home side's first-contact defence and separate response route point to a competitive margin. That's why I'm siding with Fleetwood.