Below is a series of questions to help you answer which emulation vendor's product you'd be the most happy with.

1. Does your emulation have to be freeware?
2. Would you be willing to pay 2-4 times the cash to get emulation (for convenience say, or to shed hardware maint costs) when you can buy generally Alpha hardware cheaper?
3. Does the command line scare you and you'd rather use a GUI based tool for Alpha emulation?
4. How much does system performance matter? Does emulation have to be faster to be worth it for you?
5. Does your organization have a datacenter and a person responsible for maintaining systems there, do you contract that out, or do you have a smaller org that doesn't need one?
6. How close is your IT staff to the hardware they maintain?
7. Does your OpenVMS, OSF/1, Digital Unix, or Tru64 system use either VMS clustering or Tru64 Alphacluster?

Here are some of the platform considerations to understand.

1. What OS will you want to run the emulator. The choice is Linux, Windows, or “bare metal” where the emulation installs it's own custom OS on the hardware you choose.
2. Will you virtualize the emulator in something like VMware, Xen, or Virtualbox? Each vendor has different considerations for this possibility. Some are more friendly than others to virtual environments.
3. Do you want to install on your own server or host it somewhere else?

The emulation vendors will crow a lot about their performance. Don't believe them. Even the best performing Alpha emulation requires powerful hardware just to emulate the EV6 at full speed. Matching or beating the Alpha EV7 performance with emulation is currently impossible. After I finished laughing, I'd call BS on any vendor who claims otherwise. A real GS1280 server will destroy the performance even the most powerful emulation host currently available. However, here are some performance considerations:

1. What type of alpha processor does your current server use? You can look it up on the Alphaserver wiki page.
2. What type of storage does your old server have (SAN, SCSI, IDE, etc..).
3. Do you currently have any hardware RAID controllers?

Not all hardware can be emulated. These questions represent those concerns.

1. Do you use any serial devices on your server?
2. Do you print directly from your server to a parallel or serial printer?
3. Do you have any rare or wacky interface cards installed that are critical to you? One example are memory-channel cards used for clustering.
4. Do you need a graphical (GUI) console for your business needs?
5. Do you use any hardware encryption devices with your server?
6. How much storage capacity will you need. Do you already have it on the emulation host?