Through one of OOTP's rivals, Baseball Mogul. I joined their forums maybe a month ago and there's a thread comparing/contrasting the two games.
My next stop was actually these forums first. I like reading action reports - dynasties - from different games and was really impressed with the community you've developed here, so I downloaded the demo.
It was a bit intimidating at first. The level of information OOTP offers is... ...intense... but before I realized it I'd taken my eight team league to the August 1 end date, then went into commissioner mode and started testing just how far I could tweak the league settings.
I like the customization it offers as it lets me get a lot more creative than most games built around the real major leagues. I'd say that and the aforementioned community were the biggest selling points to me.