I don't think Strat-O-Matic can be beaten. Why? Very simple answer:
THE CARDS
I haven't played Diamond Mind or APBA. I'm sure they can be fun. But you cannot beat the information you get on the cards.
Other reasons:
SOM uses scouting reports for defense ratings.
SOM balances stats against history, knowing for example that pitching gets diluted in expansion years etc...
Diamond Mind argues against the cards, stating you are trying to get a computer to mimick a parlour game. I say that is exactly the point in SOMs favor. To be able to stare at a card that sums up everything about a player is like looking at an accurate one page assessment of that player.
The bottom line is that this game has the right amount of statistics and strategy. Certainly not too little.