I also played baseball mogul for a few years before i discovered ootp. BM does hold a candle to ootp except for one thing, imo. The aging model.
http://www.sportsmogul.com/content/aging.html
I'm sure ootp has something like this behind the scenes, or it's simply random, but i would like the ability to control it. I know that there's an aging modifier in ootp, but BM lets you set it for individual players.
BM also has player deaths, which ootp needs