6 star has less hp and def so they weaker and lose hp faster ., in the end they can generate energy faster and use ulti
But 7 stars has more hp , dmg and def ))))

I've noticed that my 6-star heroes aren't doing as much damage or surviving as long as some guys with 4-5 star heroes... and my ultimates charge much slower than my opponents with less stars. Maybe same could be said of 7-star vs 5 or 6's?

Frustrating indeed when you go up against equal level opponent with less stars, and you lose because their 4 star Jasmine got off 2 Illuminates to your 1...