More seriously — I’d vote costume over just clothes. Mainly the way the vest flows over to the arms, it doesn’t look like casual street wear as much as costume flow.

Like the subtle electron path (atomic rings) traces around the fists.

The flame on the head looks less “mane” versus the one they were doing on The Flash. Makes Firestorm look less like the Elemental — and honestly, something about the face says “Jason” more than Ronnie to me. Alternately, this may be how they handle not getting Robbie Amell (if they couldn’t). Stein is there, and can call Ronnie in as needed — but Firestorm now has a pure-CGI “game face” overlayed over whatever stunt man they care to use. So Dan Cassidy can now be Firestorm.