I rag on Super Saiyan 4 for making all the characters look the same, but honestly, the same could be said for 3.
It could be said that when it comes to DBZ, if not all of anime, the most recognizable part of a character's design is their hair. And even when Super Saiyan became the standard in the cell saga, every Saiyan character had their own unique hair style while still obeying the "rules" of the form. Trunks himself has like fifteen Super Saiyan designs even though they're all technically the same form.
But again, 3 just makes every character look the same.