About 91% percent of sites that have implemented IPv6 are running Apache or Nginx.
More than 73.8% are running Linux; however this number is likely much higher as the Operating System detection failed for about 20% of sites.
IPv6 infographic of top web sites
IPv6 capability was not confirmed, the data came from prescense of AAAA dns records.
I will see if I can put together comparison statistics for the IBM Web Servers.
Online Port Scanner