I've only been to the Mandalay Bay Events Center for Barrett Jackson, which uses an end stage concert set up. I can only assume the MJ event will be the same. I "think" the Staples Center is much bigger, but I have never been there. One thing I remember specific about the seats that aren't on the floor is that the rows are kinda steep, so the person in front of you doesn't block the view with their head.
I was talking with a friend at work today and he said that he likes concerts at the Mandalay Bay Events Center MUCH MUCH better than at the MGM Grand Garden Arena.