I'm not trying to start an argument here but if you get an extension cord with an adequate amperage rating, you should be fine. If the cross-section area of the copper is large enough, the losses can be kept at a safe level. Use the shortest cable possible, too. It's probably best to only have have AWG 10 extension cords in the shop. Or maybe AWG 12.
Here's a good guide I found:
Buying Guide: Extension Cords at The Home Depot