Dash is useless and jumping is the optimal way to move even if there aren't any verticality.
Sure, the difference for non-strenght based characters is "important" but it does not worth wasting your action at all.
Images:
Seems like your claim is only true for Strength characters. Gale doesn't look like he gained any significant distance from using the Jump Bonus Action...? Maybe 5 extra feet of distance, for a ~15% movement speed buff?
Whereas the strength character got an extra ~15-20 feet of movement by jumping, for a ~60% movement speed buff.
And of course the big consideration is: "Is that extra distance worth a bonus action?" The answer to which is highly affected by
- verticality of terrain
- opportunity attacks that you might entirely skip by jumping over enemies
- surface hazards you could jump over
- what other bonus actions your character has