I think the Celtics playing in the West would be another "elite" team like the Hornets, Spurs, Lakers, and Suns with no clear decisive winner.
Celtics only have to get up for hard games once every 2 weeks. Meanwhile, in the West, practically every week you have a couple hard games.
Playing a good team almost every game takes its toll on you, I think the Celtics would be closer to 20-25 losses by now if they were in the West. Pistons would probably not be a top 4 team unless they're in the Northwest division.
Even West teams who will miss the Playoffs like the Warriors, Trailblazers and Kings would be in the Playoffs in the East. Warriors a #9 seed would probably be a #3 in the East.
Good Take!
The Western Conference runs 11-12 teams deep, the Eastern Conference runs maybe 4 teams deep.
Celtics and Pistons would be very good in the West but in the East, they're godlike.