Extreme Depth. Keeps you coming back for more.
For that reason alone OOPB will satisfy almost any baseball fan. You can look at averages, career and season, slugging percentages, steal sucesses and percentages. And that's before you even look at the players attributes (both potential and current).
There are many leagues you can manage in (although MLB is the most common choice). You can start in the R Leagues and work your way up to the big time although you can have a very average season i.e. less than 50-50 ball and still manage to get offered a job in the next tier of leagues, which is a bit of a gripe.
There's no denying that there is a huge amount of info at your fingertips and many different strategies you can employ. You can preset for simming the games or you can take control of the game and set you strategies on the fly.
As a beginner there is a heap you can get lost in and knowing a bit about baseball (sadly I don't know much at all) would stand you in good stead, but there is the option of buying up all the big names and simming the season to see how they fare.
While many might find this hard to get into many will love this game. With the amount of depth here the die hard baseball fans will be kept happy long after the world series is over.