Practice ones that you lack technique/skill in, or you "need" in the repertoire you're playing.

And divide your exercises into mechanical exercises vs musical exercises:

mechanical: Hanon (uh.......), Pischna (transposing common pattens), Dohnanyi (finger independence), Phillips (finger independence), earlier Czerny (speed and dexterity), Liszt's Technical Studies (best one- every possible combination of notes/technique in all keys in 12 volumes from one of the best pianists)

musical (in general order of difficulty): Burgmueller, Heller, later Czerny, Cramer, Tausig/Clementi, Brahms, Moscheles etudes, Moszkowski etudes (good preparation for Chopin), Chopin posth. etudes (polyrhythm), Chopin etudes (variety), Debussy (variety)

repertoire that can be exercises: Clementi/Kuhlau sonatinas (scales/arpeggios), Bach Inventions/Sinfonias (hand coordination), Chopin waltz (chord inversions), rags (jumps and syncopation), Bach fugues (polyphonic pieces)