Has not much to do with fenestron vs tail rotor but simply with a relatively low power tail rotor/fenestron… (like an ec120’has…) with both you run out of them at some point. With aircraft with larger fenestrons you hardly notice any difference if any at all between them and a normal tail rotor. Fenestron of an H145 is for example much more powerfull than the tail rotor of its predecessor (BK117 up and including C-2) Even Bell and Leonardo who always argumenten agents “enclosed tail rotors” now introduce them on their Invictus and AW009… Comanche also had one and flew 70kts sideways easily.