I’ve recently jumped into a game of Dragonlance despite the fact that all I know of D&D stems from Solasta & the old Neverwinter Nights games. I came to play an Elf Fighter that I want to subclass to Echo Knight. The GM was so friendly to let me rethink my choice of cantrip, which I humbly seek to be advised on. My current favourite is Booming Blade, which I find mixes well with the ability to move out of the current melee by switching with the echo. It also scales in damage the same way I’d receive extra attacks, so I won’t be missing out on much damage in my view. What would you choose, and why?
A fighter using Booming Blade means not benefiting from its Extra Attacks. It's nice at low level, but replacing 1 or 2 of your swings with some damage if you hit is situational.
See this analysis.
There are utility cantrips. For use in combat I'd pick a ranged damage spell and Mind Sliver is only Verbal so no need to free a hand up.
sounds cool! My GM also gave me your consideration - I don't profit from more attacks, which is true, but! I'm only using a longsword and shield, so I do D8s of damage, which is also how Booming Blade scales, so I'm "only" missing out on the +4 Strength Bonus (currently).
Plus I intent to regularly make use of the extra damage Booming Blade gives by disengaging via echo. At least in my mind.
Don't get me wrong, I'm not trying to be smarter than what you suggest (I can't - I'm a noob), I just use the opportunity to check wether my plan would work in the first place.