Great article that talks at length about how hardware architecture DOES impact virtualization.  If you’re not familiar with NUMA this is a must read and in general a very well written article.  It might also help you troubleshoot poor performance of a VM by helping to define some of the metrics you can monitor to measure percent of remote memory being used.

http://frankdenneman.nl/2010/02/sizing-vms-and-numa-nodes/