While Kroll is basically virtual button mashing and a shake, Hero Of Sparta varies up the control.
There is a virtual joystick on the left side, which works quite nicely. Sometimes on Kroll I would miss pressing the left or right button, which gets somewhat annoying.
There is an attack button and a shield (defense) button. And whenever you need to jump, a jump button appears.
Some of the gameplay is taken straight out of Kroll, like the special move which you do by sliding the shield button. It's a little less annoying than shaking the iPhone as in Kroll. Plus, with bosses you can do special things like stabbing him in the throat or decapitating him just by pressing certain buttons on the screen, which is pretty much a copy of Kroll.
What I like about Sparta is that you can fight in 360 degrees, whereas Kroll is a scroller.
And in Sparta you can get life back by finding a green crystal. I was annoyed that in Kroll you have no chance to get back your life bar.
I'm going to do a video sometime today.