TLDR: Level 5-6 Bladesinger getting level 3 spells and 2nd attack — should I upcast Shadow Blade or cast Haste? Or do something else?

.:.

I’m having a very good time playing a melee frontliner Bladesinger Wizard and already got very good advices to potencialize my defensive capabilities with the right feats + spell selection.

Now in terms of offense, there are a plethora of good choices. To give some context, my character is at level 4 and my usually go-to setup is Shadow Blade + SCAG cantrips (sidenote: my DM loves swarms of mooks and minions, so I get myself using GFB a lot instead of BB).

Moving towards to level 5 where I’ll finally get access to the wonderful world of level 3 spells and at level 6 when my 2nd attack comes into play, what would be the ideal choice:

1. Upcast Shadow Blade?
2. Cast Haste?
3. Something else?