You confused me, I assume you mean EARTH ground versus electrical equipment 
     ground??  If this is the case, either will be sufficient from both a 
     personnel safety and ESD safety standpoint if installed correctly.
     
     If using earth ground by inserting a grounding rod through the floor into 
     the earth, the ground rod must be electrically bonded to the electrical 
     equipment ground (I believe this is a National Electrical Code 
     requirement).  This is especially true if personnel are working with 
     electrical equipment (soldering irons, etc.) while connected to ground.  If 
     there was an equipment failure where a "hot" wire contacted an electrical 
     ground (i.e. through the equipment chassis) that charge is going to seek 
     the least resistive path to ground.  If there was a lower resistance to 
     earth ground, personnel could be exposed to lethal voltage.
     
     However ESD wrist straps/cords must have a safety resistor installed to 
     limit current flow in case this happens.  The wrist straps and cords should 
     be tested daily to ensure that the resistor is functioning correctly.
     
     Basically if facility electrical ground is per electrical code, that's the 
     best way to go from both a safety as well as convenience standpoint.  You 
     might want to ensure that there is very little difference between 
     electrical ground and earth ground prior to committing to one method or the 
     other.
     
     Hope this helps, if I am not clear on something, let me know and I'll 
     elaborate more (the boss gets mad when I spend 30 minutes writing one 
     E-Mail)
     
     Steve McBride
     Frontier Engineering Inc.

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