Hero is faster than D+D 4th by a MILE.
The only thing that makes 6th a litttle slower are two powers with stop signs, and if you don't use them, combat runs pretty quick. Damage Negation is a logistical nightmare that gives me fits, especially if more than one person in the group has Damage Negation. I banned this power. All it takes is one area effect and combat slows to a crawl. The other is the removal of Transfer from the game, clearly a mistake. Now it's Drain, Aid, cobble together results. This is the worst idea ever. 3 rolls to resolve instead of 2, and the laws of superhero physics go completely haywire. You can gain more than you take away easily. If this is my suite of super-abilities, as a player, you just became a jerk. "I drain him! I aid me! And I also aid this guy because the aid is area effect!"
GM: Thanks, Captain Confusion! I knew I could count on you! How did you get more power than you took away from him?
I run Hero 6th because it is an improvement over 5th with the exception of 5 things. Aid/Drain (Transfer was better), Growth (4th edition Growth was better), Damage Negation, END + STUN vs. Defense Levels, Replacement of " symbol with Meters.
Of these, two are combat decomplication (Why would you add new powers or remove powers that slow combat down?), One is stylistic differences, One is "I only run mapless combat when forced, and the meters issue means you can't use a 1-1 ratio. 1 hex=2 meters. Now you have to pick the scale of the map before you start every time."
The last one, Growth, is my pet peeve. Now, Growth is degranluarized.
Which means this: It is harder to build the most basic characters, i.e. a character whose main power is the ability to change his size.
Shrinking is another pet peeve. 6 points per level for the benefits it grants? More than three eats your average bell curve and spits it out.
I have fifty pages of house rules. This is painful, but it's better than the alternative.
So why run Hero 6th? Because I always run in the latest edition of the game. It gets you published, spreads your name around and builds your game design cred so that you can write novels and have people know who you are. That's my goal in life.