>I am pretty sure that running home versions of Windows in contexts like this is against the Windows TOS.
For Windows, Microsoft restricts features but not what purpose you can use it for if you're talking about Home versions. For Office however, the home version actually has restrictions in the TOS that limit use to only noncommercial purposes. For a standalone Windows box that is only used for some lab equipment and will never be domain joined there's a good chance that there's no technical reason to go with Windows Pro over Home.
For Windows, Microsoft restricts features but not what purpose you can use it for if you're talking about Home versions. For Office however, the home version actually has restrictions in the TOS that limit use to only noncommercial purposes. For a standalone Windows box that is only used for some lab equipment and will never be domain joined there's a good chance that there's no technical reason to go with Windows Pro over Home.