The finger patterns are the same on each instrument...it's just that 'all fingers down' on a descant or a tenor is C, but on a treble (or bass or sopranino) the same finger pattern is an F.
Descant and tenor have the same fingerings for the same notes - the tenor is an octave lower (and bigger than a treble). Tenor lowest note = middle C, treble lowest note = F above that, descant lowest note = C above that.
There are some exceptions to the identical finger patterns at the extremes, e.g. bass and garklein. However, those tend to vary by instrument with no hard-and-fast rules like 'Eb on a bass is always 0135' (it is on my bass, but it won't be on a different brand bass). Descant, treble and tenor will almost always have the same set of finger patterns.
Treble has by far and away the largest repertoire available, if that makes a difference to you. If any charity shops near you sell sheet music, any recorder stuff you pick up there is almost inevitably going to be descant (but also playable on tenor - descant is written an octave lower than played, so in written music descant and tenor both have a 'lowest' note of middle C).
Dolmetsch have an
Online Recorder Method which is worth a look.
Edited: in order that it made some sense...