I'm partial to the new Augie field as having the best playing surface...not the toughest place to play though (since students cant drink and get rowdy like @Carthage & @Millikin). I think Carthage can be a very tough place to play due to it usually being sorta cold and windy. IWU and NCC have great complexes but I think Augie's field is better (biased view).
North Park's new field is crazy. It's part of the football/baseball/softball megafield. Right field fence is the football stands which runs straight to center. Then, from there it's like playing little league in left field where behind the left fielder is the softball field. If memory serves me right, the only fence they have in left is about 450 away and is the 3rd base backstop of the softball field. Also, they have that "play" turf stuff that you see on football fields. I was never a fan of that for fielding grounders because the ball seemed to skip off the rubber marbles in the "grass". And little cutout dirt spots for bases never did it for me.