Depends on the situation.

Shadow blade is easy:
Cost - BA, concentration and spell slot
Benefit - 2x (3d8 +4) = 35 dpr per round and ADV if dim or dark (and a really nasty BB Op Att if you get lucky)

Haste (self) is harder because there is so much to consider:
Cost - Action to cast, conc, spell slot, 1 round of lethargy
Benefit - +2 AC, +1 weapon attack or Dash/Hide/Disengage

Now what do you do w/ Haste?
First round you cast it and then get to make one weapon attack (1d8+4) or DHD (a weak round usually).
Following rounds: Cast spell or attack x2, and 1 weapon attack or DHD.

So do you can cast fire ball, and swing once (or DHD) on following rounds.

BB/GFB plus extra attack is better than attack x2 (assuming hit and rider triggers), etc. For simple DPR, BB/GFB + extra attack = 30 dpr so less than Shadow Blade, but you also have many other options ...

So it depends (damage resistance, your AC, their AC, lighting, to hit bonuses, etc)