Two things about CO compared to CoH. First, Cryptic learned three lessons developing CoH they put into practice in CO. One: avoid escalating returns in mechanics (vis-a-vis Defense and Resistance in CoH). Two: Unrestricted AoE is bad. Three: hard control is worse. The power levels in CO are significantly lower than they are in CoH for the most part because of those three reasons.
Second, CO's power system framework is far less forgiving than CoH's. In CoH, you could literally make a random build using dice and a dartboard, and it would be wonky and weird, but stand up to standard content reasonably well. Players could build conceptually or cosmetically and still be playable. In CO, that's really not true. And CoH's enhancement system is far more transparent, and that's saying something because CoH's is unnecessarily cluttered with trivial and inconsequential detail (sometimes I wonder if the fact that Mathematical Proof salvage is a trivial non-entity that most people discard was a deliberate gag by Castle, but I believe he inherited the names of things). CO's gear system makes CoH's gear system look like playing tic-tac-toe with only the X's.
If you are an MMO veteran that likes playing build-jockey, its not necessarily difficult to make powerful builds in CO. But unless you basically straight-up copy someone else's ideas from the forums or think Excel is a past time, a non-veteran MMO player is only going to make very powerful CO build by accident.
Its in many ways a more balanced (in the player vs environment sense) and controlled environment than CoH ever was. But its also, at least in my experience, a less rich and interesting superhero environment. I think balance is important, but I think a superhero game needs wild and crazy more than balanced. I firmly believe you can have both if you design carefully enough, but CoH and CO demonstrate what happens when you can only have one, and each has a different one. I think the CoH experience is the better one.
I think it's a stupid "lesson" to feel that hard control was bad, because it set them up to later make crowd control completely without any use, because they kind of had the attitude of a scrub mentality when many rpgs had hard control in them. Just you needed to provide means to counter crowd control that was modestly available. CO initially had solid cc but CC got nerfed so much in the hands of the player, while also buffed in the hands of mobs when players ignored cc resistance.
The, game was kind of setup to railroad players into only very specific builds for a number of the above reasons. While the second lesson was fine, and the first was ok, the third one just made sure that crowd control was largely unneeded later, when pvp-scrubs would complain about cc in pvp.
Counters and counter-counters are good, but not providing that and just removing something instead removes depth, which is what scrubs want ultimately. They also ended up going down that path of making everything generic with buff/debuff mechanics becoming weaker and weaker, which eventually lead to just damage/healing/durability we see today. Everyone is either durable as superman, or as devastating as he can be, but never ever both, or just somewhere in between but ignored in some team situations. But in one mission(the fire and ice rampage) likewise everyone needs "that healer" to keep them alive. So we don't really have the true "super hero" experience, consequently.
While city of heroes was kind of, well if what they say of fallout 1 and 2 is true, it was more a true super hero game as an mmorpg could also be truer to an rpg. Your chosen power sets truely changed your strategy alot. There is no difference in CO between fire, lightning or ice other than energy unlock mechanics and a couple other small differences. In city of heroes energy blasts tendency to knock enemies back, electrical blasts tendency to drain endurance, and ice blasts tendency to slow movement severely and also it's actual crowd control abilities make those three sets function very differently than fire blast. OR storm summoning was very, very different to force fields ect.
City of heroes could be better looked at in comparison to the x-men, it was a team-game that had a huge, wide array of abilities and it was more interesting to find out how a hero with "X powerset combination" would deal with a bunch of badguys vs a hero with "Y powerset combination", while CO is more like batman or superman, or even just superman, you know he'll win, but it's very very rarely a question of how, especially if the writer never includes kryptonite and lets superman just plow the badguy. In fact, most CO gameplay is just plowing badguys with the same tactics at differing speeds, end a fight faster or end it slower but always at full health.
Edit: Or even slower and with less health because your chosen powers lead to both less dps and offense simply because they lack things like the critical energy unlock or just do less damage than other powers of the same types.
