Arial Black
Adventurer

My CoS PC has just hit level 2. She started as a fighter with TWF style using sabre & stiletto (scimitar & dagger). From the start she was designed to multiclass into warlock and thereafter be Ftr1/WarX, using hex to make TWF work.
I am going to choose prestidigitation as one of my two cantrips (for RP purposes), and I'm choosing between Booming and Greenflame blade for the other.
I already have vicious mockery (from the Devil's Tongue variant tiefling ability from SCAG), and I'll get eldritch blast when I hit Ftr1/War4 (the same time as I get the Warcaster feat).
Initially I didn't consider either SCAG cantrip, as using either denies me a bonus action off-hand attack, but then I realised that there will be rounds when I cannot or will not use my bonus action to make an off-hand attack (like when I only have one weapon in hand at the start of combat, or when I need to either cast or change the target of hex), and on those rounds I could make use of one of these two SCAG cantrips.
But which one, and why?
I am going to choose prestidigitation as one of my two cantrips (for RP purposes), and I'm choosing between Booming and Greenflame blade for the other.
I already have vicious mockery (from the Devil's Tongue variant tiefling ability from SCAG), and I'll get eldritch blast when I hit Ftr1/War4 (the same time as I get the Warcaster feat).
Initially I didn't consider either SCAG cantrip, as using either denies me a bonus action off-hand attack, but then I realised that there will be rounds when I cannot or will not use my bonus action to make an off-hand attack (like when I only have one weapon in hand at the start of combat, or when I need to either cast or change the target of hex), and on those rounds I could make use of one of these two SCAG cantrips.
But which one, and why?