Synth vs Bandsintown
Bandsintown excels at tour alerts and ticket links. Synth excels at seeing who else is going to a show and messaging them. They solve different problems.
Bandsintown
Strength: follow artists, get notified, click out to tickets.
Synth
Strength: mark a show, see members interested or going, message, review nights out.
Use both
Follow artists elsewhere; use Synth when you need a person for the same night.