Do you mean musicianship, technical proficiency or something else?
Well, I don’t expect anyone to agree because Genesis fans…but if you look at the supreme ease with which they play live around IT, it seems that they are the most on top of their game at this time, with both the newer and older songs. The older songs may be more complex, but that doesn’t make older Genesis more technically proficient. It just means the songs were more complex. Yes, the drumming is more bad-ass on The Lamb, but I suspect IT-era Phil was more at the height of his ability.