Yamaha DTXpress/DTXplorer/DTXtreme

Hi there---I am considering buying the Yamaha Ds-11 drumset.  I am 
getting it brand new for $1100 since I work for Yamaha.  However, 
this is my first set of electronic drums and I am unsure of what to 
do. 
First---the Rolands to me (studio set--rubber pads also) seemed a lot 
tighter---faster and better response.  It seemed to pick up ghost 
strokes much better than the DTX or the DTXpress.  
     1.) Why does the DTXpress and DTX not pick up ghost strokes 
     2.)  The response of the hi-hat was very slow and delayed
           why???
     3.)  If i bought the DS-11 set without the brain---could I use a 
Roland TD-8 brain and 
how would it sound compared to being played on a roland kit???