Chose parks based on these factors.

HR's allowed vs lefties and righties, as well as Batting average allowed. I believe these are the 3 most important factors.

If you have hitters with high averages(say .280) and your pitchers allow low averages(say .230), having a park that boosts average(say 10%) will give you an advantage. You would gain .028 batting ave., while only giving up additional .023 batting average, a net gain of .005 BA.

If you have lefty power hitters, get a park that helps those hitters(just make sure your pitchers don't give up tons of HR's to lefties).

I like to see what my pitching staffs weakness is, then chose a park to help them.