Each of these has some good attributes and some room for improvement.

I think the choice will depend more on what is appropriate for the customer environment it is in.

Initial Installation
ESXi: Easy. Create a CD from ISO, pop it in, click a few keys, and you’re done.
Hyper-V: Easy. Roughly the same install process and time as ESXi.

Basic Hypervisor Configuration
ESXi: Easy. The text menu is fairly intuitive and fast.
Hyper-V: Easy. Pretty much the same as ESXi.

Advanced Hypervisor Configuration
ESXi: Medium. Easy to download and install the VI Client, but once you get there, it is not immediately apparent where to go to do things and what needs to be done. The UI is a little clunky, but it has GUIs for everything you need.
Hyper-V: Difficult. First, getting the management console isn’t well advertised, and takes some digging. Once you get it installed, you have a nice GUI – but you only get a few GUI settings. If, for example, you want to manage your storage, you have to go to the console (or use RDP to get there), and use command-line DISKPART to partition and format disks. Ugh.

VM Creation and Editing:
ESXi: Easy. Has a nice wizard that takes you through it, covering the key basic stuff that all VMs need. You can further edit the VM afterward.
Hyper-V: Easy. Same as ESXi, only it looks different.

Granularity of Settings:
ESXi: Excellent. There are all kinds of interesting options you can set. The hard part is figuring out which ones to set, and what values to put in there.
Hyper-V: Good. You can do most things the average IT admin can think of, but it is not as detailed as ESXi – At least, not at first glance. There may be some command-line things that you can do to get crazy complicated – but where is the documentation?

Stability:
ESXi: Excellent. I’ve only had a few errors with ESXi, mostly when I think it is taking too long to do something, and I get impatient and start clicking other things.
Hyper-V: Very Good. It gets a “very” because it does well for a 1.0 product. I’ve had one blue screen during setup when all parameters were the same as half a dozen successful test runs, and I have had to end task on the management console a few times – mostly when it is taking too long to do something and I suspect that the console is hung up – and I am right.

Ease of Migration:
ESXi: Mixed. It is easy to get things converted to it using VMware Converter, but moving files around is painful with the Datastore browser, and you have to “hack” the console if you want to use a file transfer tool such as WinSCP or commands native to the OS.
Hyper-V: Mixed. System Center Virtual Machine Manager is in BETA and not easy to work with, but moving files around is easy. You can use Windows Explorer to connect to the server’s file system, or ROBOCOPY, or your favorite SMB-based file management tool.

Since this article was written, I have learned some additional things about ESXi vs Hyper-V that may further impact the choice:

Console Access:
Both packages offer console access to the VMs, but they are significantly different in one important way: The ESXi console works pretty well in most environments, including when you are using Remote Desktop to control the management station. Hyper-V, on the other hand, has a serious problem with this: the console will not capture the mouse if you are accessing the management station via RDP, unless you have installed the Integration Tools. Installing them without a mouse was painful – even with keyboard shortcuts.

Snapshots:
ESXi seems to manage snapshots well, and when you remove all smapshots, it cleans itself up well. Hyper-V does not clean up snapshots well. I received a detailed description of the problems from a reliable source who has been working extensively with Hyper-V recently. Read about it here.

64-bit Requirement:
ESXi has a short list of machines that it is compatible with, and with some extra research you can find some additional hardware via anecdotal evidence – but it works with both 32-bit and 64-bit hardware. If you have an older machine, you can use it for a low-powered VM for a specific purpose. Hyper-V requires 64-bit. I suppose this drives newer, faster hardware which is good, but somewhat limiting.

Management Station Requirement:
You can load the ESXi management client on just about anything. For Hyper-V, your management station needs to be Vista or Windows 2008. Again, quite limiting.

For an I/O performance comparison between the two hypervisors, click here.

Tags: ESXi, Hyper-V, Usability