What is the difference between Rome 390 Boss and Rome Targa?

I just bough a 2011 Ride DH2 Snowboard and wanted to know what bindings would be better for it. I ride All the mountain, a little more leaning toward the park. I wanted to try the Rome Targa or the Rome 390 Boss. Im 5'11 and 150 pounds. Dont just say targas or 390s are better give me some explanation. I know the main difference is the flex but how much is the difference? Also im thinking the Thirtytwo Lashed boots should go well with the set. Thanks for your responces