Can I use AMP plates with Agrobacterium? - (Feb/08/2007 )

My Agrobacterium carries Rifampicin and Gentamicin resistance helper vector. My vector confers Ampicillin resistance. To grow this Agro and select the transformed with my construct, do I have to use Rif/Gent/Amp plates or Rif/Gent/Carbenicillin plates? I’ve heard that Agro must to be grown on Carbenicillin instead of Ampicillin. Why?

Carbenicillin is more stable compared to amp. And less heat sensitive compared to amp. And of couse carbenicillin is much more expensive though.