I’ve had this question about a kazillion times by now, what’s the difference between ESX and ESXi. How do they compare… Can I do this with ESX, can I do that with ESXi.
Here’s the answer! This KB article contains a table with features and a description of what you can and can’t do in VirtualCenter. Check it out, it’s definitely worth reading.
And in addition to that, it is possible to do most configurations post installation via powershell. Check this topic on the VMTN forum by Lance!
Post with links to both 3.5 and 4 comparisons as well as other articles: http://www.unitrends.com/weblog/index.php/2010/02/20/backup-vmwares-roadmap-and-esx-versus-esxi/