Which Vista

You can "move" the retail install from machine to machine, but with either license, you can only have it installed on one machine at a time.... you can not install retail on multiple machines at the same time.
 
If you mean multiple computers at the same time, neither one will work.

If you mean over time, as in upgrades, technically, the retail is what you want, but many people are able to call in an OEM license to reactivate it.
 
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