My City of Heroes “main” was a Blaster, but Defender was the only archetype for which I had multiple level-capped characters, three in this case. Were I to go back, I would be all about Controllers, of which I left at least three in the mid-levels.
For me, this was all about diversity of play. Blasters and Scrappers are damage dealers, Tankers are tanks. While each archetype has several power sets, all but one of them are usually more or less the same thing: damage with some minor effect attached. The differences between Ice Blasts and Fire Blasts and Dark Blasts were small unless you specialized in those side effects rather than in damage. I did that on my Defenders, making their attacks even more support, but you rarely want your primary damage class to be ersatz-support.
The support sets, however, differ quite a bit. You could have damage prevention through Force Fields or healing through Empathy. Darkness focuses on reducing enemies’ effectiveness, while Radiation mixes buff and debuff effects. Kinetics is a ridiculous stack of buffs and debuffs. The control sets use a common template of holds and other control, but each varies and also comes with a few trick and support abilities; Controllers got a control set and a support set, so you could see some real diversity in what they brought to the table.
The only interesting thing about trying more than one version of the non-support classes is the one odd power set per archetype. Spines is the Scrapper melee with AE and range. Ice is the defense-based tanker armor with two taunt auras and a bunch of debuffs. Some Electricity Blasters went melee, relying on endurance drain to keep the enemies from doing much. And in powerset proliferation, which opens up more combos, and a second tank or DPS might be interesting.