If we're talking about an NBA player being equally good at baseball I'd choose Lebron James in a heartbeat, over and over again. The irony is I would never want him on my NBA team but I think his selfless, all around, star powered personality would be a better fit for baseball believe it or not.
Lebron James might be that guy who passes the ball in the 4th quarter and is a little less reluctant to take over a game like other elite players but the baseball manifestation of James to me is a guy who does it all. A guy who can hit .300, hit 30 HR's, steal 30 bases, and play elite defense. And his primadona attitude is the kinda attitude baseball might need right now and believe me.....I'm the biggest James hater out there.
On the other hand, he might be demanding 40 million a year.