I think people are overstating the East-West thing a bit. If he stays in the East, he'll have a much easier path to the finals, but he'll have a tough finals matchup. If he goes to the right team in the West, he'll still be favored to get to the finals, albeit at less odds than in the East, but he'll have a much easier opponent.
A LeBron-led team in Golden State, LAC, Houston, Dallas, or Phoenix isn't going to lose in the first round, will be heavily favored in the 2nd most likely, and will have a tough matchup in the WCF, and then an easier one in the finals. Is that much different than an easy first and 2nd round in the East, and then facing the Bulls, Pacers, Raptors, or Wizards in the ECF? Remember, any team he signs with in the East (besides the Bulls) won't be nearly as good as one of the West teams.
Here's some hypothetical numbers.
LeBron returns to the Heat or goes to Cleveland. You'd probably think his teams would have a roughly 95% at winning in the first round, 90% in the 2nd, maybe 65% in the ECF, then 50% in the F. .95*.90*.70*.50 = ~30% chance at a title.
Westcoast LeBron:
.85*.80*.60*.80 = ~35% chance at a title
If I were LeBron, I would just focus on what team would be the best, regardless of competition. When you're as good as LeBron right now and have some help, there are only going to be 1 or 2 teams that have a real chance any way, and you'll probably have to face them regardless.
