I'm cool with either.
I think "5-4 Fighting" is probably more appealing to people browsing for groups, but "Team 54" is better when you're using it in a sentence: "I'm a member of Team 54."
Maybe officially "5-4 Fighting," but all the cool kids will refer to it as "Team 54"?
In honor of my favorite team, I've changed my profile pic.

I like Team 54 better than 5-4 Fighting. The name "Team 54" is more intriguing, arousing the curiosity as to the meaning of 54. It's a different name but it carries the same meaning; and our logo says it all, five fingers ball up tightly into a fist for fighting. Not to mention, our team's discription reads as follows: