Never used or seen the flex.  I bought 8 used Yetter fixed for my JD 7300 planter last spring.  I like them.  I can even move enough trash to no till c into c.  It takes a little trial and error to get the units to the depth that I want on each field, but I don't farm half the nation so that is OK with me.  They only cost me $1,600 total so I am happy. 

Row cleaners and closing wheels are like ladies, each person will have their own preference.