Once you get past a certain level it becomes all about power supplies. It's easier to fit over the top power supplies in separate components.
Are integrated amps technically better than separates?
I'm assuming we are talking same class of amplifier and the integrated has the features you want. I'm thinking the integrated could actually be an improvement over separates due to being a more "direct" connection. Taking away the flexibility factor of separates, is my line of thinking correct?