Yep, in the past I made some off the hip comments on all wire being the same resistance, but after going through a few spools of MD wire I have noticed a slight drop in Rm's. I verified my suspicion by checking resistances on 1 foot lengths of different gages of MD and alltronics wire, and the MD wire consistently came out a few uOhms lower.
I'm not 100% sure, but I think MD wire is polyamide wire. 200C makes it definitely an amidester. It's slipperiness and resistance against abrasion makes me think it is likely polyamide versus a plane amidester? Then again, I haven't played with a known sample of plain amidester wire. Powerwerx has good prices on polyamide wire, but they only have even gages. Dan's stuff costs a few bucks more, but he carries odds. I don't mind paying a little extra to support a fellow hobbyist. Of course if I weren't poor, I might find out where my local repair shop buys their 5gal buckets of polyamide wire.