Difference between upgrade and clean install?

Is there a difference between a clean install of Windows 7 Professional and upgrading from Windows 7 Home Premium to Windows 7 Professional?

I ordered a computer and I require Windows 7 Professional, but they accidentally sent me one with Windows 7 Home Premium. They have offered me a Windows 7 Professional Upgrade disk as a resolution to the problem, but I'm worried an upgrade may not be as stable as a clean installation and I'm not sure if I should accept this resolution.

Thanks in advance for any help,
John.

Well naturally the upgrade will leave some fluff from the previous install which Professional may not need, but depending on how long you've had/used the computer (it sounds like it's fairly new for you), the difference will be minimal.

No, there should be no difference after using Anytime Upgrade to simply insert the Professional Product Key which only unlocks the few extra features. Windows Anytime Upgrade - How to - Windows 7 Forums

You may however find these steps helpful to Clean Up Factory Bloatware - Windows 7 Forums.

Depending upon how much bloatware was larded in by the maker and how it cleans up you may choose to do what most tech enthusiasts do and Clean Reinstall - Factory OEM Windows 7.

Either way capture a Win7 backup image of the upgraded OS afterwards to use in place of the double-reinstall. Backup Complete Computer - Create an Image Backup