After thinking more about the OP's post, my only thing is that basketball depends so much on Team play. Throughout the thread, there have been so many scenarios listed that it is hard to quantify it all.
So many "what ifs."
KG brought a defensive mindset to this team. Him getting here was definitely the "Other Shoe" that had to drop. He wasn't going to come here until Ray was acquired.
To say who is better or more skilled is not Boston's way. It is not the team I am accustomed to watching. That, to me, is the beauty of what was accomplished in 07-08, and kept us in contention for the last few years.
That chemistry is what has made the team here so successful. It's the same chemistry that - say - MIA lacked while they crumbled in DAL last June.
To me, it is never about who is better - it is about how players fit, how they compliment each other.
When the Basketball Historians look back on the NBA, they will compare "Stars that came together via trades or off-season signings", and they will say:
"What the Boston Celtics accomplished in 2007-08 will NEVER be done again." MIA came close, but were not ready and were too young.
The Clips somewhat fall into MIA's category, as do the Knicks. None of these teams can copy that success.
It is never about who is better. That's not Boston.