The magical team that is better than Golden State just doesn't exist. The options LeBron appears to be considering are:
Cleveland: Lakers would almost certainly be better IMO
Philly: They could compete with the Warriors if Philly were willing to trade Simmons, but they won't so they probably can't.
Houston: By the time they make the financials work, the supporting pieces probably wouldn't be strong enough, but they can't be completely written off either. It sounds like LeBron plans to opt out of his contract which will make it basically impossible for Houston to get him though.
Considering the 76ers understandable reluctance to trade Simmons and the financial hoops that Houston would have to jump through, I think the Lakers offer him the best chance at competing for a title unless he suddenly begins considering other sign-and-trade/opt-in-and-trade scenarios like maybe the Celtics, Nuggets, Bucks, etc.