Comparison between esxi4 and 5 - http://www.vmware.com/products/vsphere/esxi-and-esx/compare.html#understand
with description and more details - http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=2005377
Great guide about new method HA http://blogs.vmware.com/uptime/2011/08/vsphere-ha-50-best-practices-guide-now-available.html
Please, don't forget the awarding points for "helpful" and/or "correct" answers.
Mauro Bonder - Moderator
1 person found this helpful
If you are interested in the new design and the features of HA, DRS, ... I can really recommend "VMware vSphere 5 Clustering Technical Deepdive"
by Frank Denneman, Duncan Epping.