There are several things one must take into consideration when trying to figure out who would win the match up between the Lakers and the Heat.
Things such as intangibles, luck, officiating, health, and home court advantage can affect the outcome of this match up. Looking at this match up as a 7 game series, here is what I think is the deal:
Intangibles: Passion, hunger, chemistry, attitude, and leadership will all come into play. The passion should be equal, but the hunger edge has to go to Miami. Chemistry is something the Lakers already got down, with the additions of Barnes and Blake not expected to change that. The Heat must gel but I do expect them to be good once the playoffs the start. Leadership is present on both sides. Kobe and LeBron are vocal leaders and players such as Artest, Bosh, Wade, and Fisher provide their own ways of pumping up their respective teams. Both teams will have attitude so I expect a bit of a brawl at some point.
Luck: Well luck is luck.
Officiating: The Lakers have players such as Kobe and Gasol who can draw fouls. Artest is a technical foul waiting to happen though. I know he has chilled out, but the guy still causes mischief here and there which may hurt his team. Still no one draws fouls like Wade and LeBron, they might live on the stripe. Bosh is also a guy who can get to the foul line. Miami does not have a wild guy such as Artest, so the officiating may tip in Miami's favor.
Health: The Lakers have been a relatively healthy team and so has Miami. Kobe does have small nagging injuries and we don't know when they will really start to affect his game. Bynum is the biggest concern but the rest of the roster is usually fit to play. Wade has been 2 years straight healthy with no problems, LeBron is just a freak. Bosh was injured a bit last year but he has no real injury concerns. Big Z is way passed his injuries, and the rest of the roster does not really call for concern in that area. The Lakers are not old by any means, they are just the older team, so Miami may also have the edge here.
Home Court: This one is up for grabs, because it all depends on how their seasons turn out. I don't think Miami will win 72 games but I think they will end up with a better record. They are going to be pumped and in the mood to overwhelm the opposition. I see the Lakers losing 4-5 more games than the Heat, giving the Heat home court throughout the playoffs and the Lakers having home court until the Finals.
Winner: In all honesty, I think the Lakers are and should be the number 1 contender for the title. Back to back championships, and the most complete team in the league. BUT Miami does have 3 true elite players that are too difficult to match up with. In a 7 game series, Miami will be too much to overcome. Say what you will about the rest of the roster, but I think some people just do not understand what having LeBron, Wade, and Bosh on the same team truly means. It is a nightmare for the opposition. The Lakers are a great team, truly awesome, and can still play with any team. Kobe is great and I can't help but admire his game when I watch BUT: Miami wins the series in game 7 by about 8-10 points and earns their second championship.