For Altissimo, the more fingerings that get the notes the better.
For some Altissimo notes I have 3 or maybe more different fingerings.
The only problem with the high F# key Altissimo fingerings for me are that they seem awkward for changing quickly to other Altissimo or normal notes.
To go from Altissimo F# using the high F# key fingering to Altissimo Ab using the Front F fingering is awkward and it's much easier to go from the Altissimo F# fingering using the Front F fingering to the Altissimo Ab using the Front F fingering.
The Tenor Altissimo G using the high F# key fingering is not that hard to play but the Tenor Altissimo G using the Front F fingering can give some players problems and it often needs better voicing by the player to play it and the Teenor Altissimo G using the Front F fingering is generally more useful because the fingering bleends in with other Altissimo fingerings pretty well and can therefore be used to play faster Altissimo passages.