Well, decent competition I suppose. The Sonic will be significantly cheaper and I am betting a 1.4t manual will "wow" you in comparison.
the veloster i just looked at in illinois was listed at $18,100, including destination. the absolute cheapest sonic 1.4 LT hatch will be $17,200 ($17,500 if you add the connectivity that the veloster already has).
looking at the veloster forums, most folks looking at the veloster are thinking more along the lines of more sporty looking cars as competition.
for 95% of buyers the sonic will compete against all the other subcompact economy car out there.