They're actually both the same flight speed and teleportation distance.
To answer the OP, yes, technically Mystic Flight is better than Fly because it comes with Translocation and that's only difference between them. However, powers were always balanced in their sets as a whole, so... is the Sorcery pool better than the Flight pool? THAT can really depend.
Sorcery comes with a few powers the normal travel powers don't:
Buff: Spirit Ward [Ally, +Absorb over time]
Ranged Attack: Arcane Bolt [Ranged, Moderate DMG(Energy), Foe Knockdown]
Buff/Debuff: Enflame [Ranged Friend/Foe, Special]
Self Buff: Rune of Protection [self, +Res(All Dmg, Hold, Sleep, Immobilize, Knockdown, Disorient)]
That makes it quite a bit different than Flight Pool...That is also extra powers that can take up your own power slots. But, if you're a melee AT or a range AT, these powers can fill holes.