I voted fun but I don't like this question. You can have balance AND uniqueness, you just have to balance considering more factors and be vigilant with how and how much classes are being used. Not every class needs to do everything, but if one class doesn't bring as much X, it should bring more Y and if it has low X and Y it should have a ton of Z.
Look at how hard warrior has to work to provide quickness while having subpar dps and no utility, compared to power quick scrapper with ok quickness and ok dps and some utility, compared to firebrand with easy quickness AND good dps AND strong utility. In this case, if condi firebrand is the baseline, scrapper should be buffed somewhat and warrior should have huge outrageous dps. They all get to be unique while still viable compared to each other.