I've never used plastic reels, but IMHO in stainless, 120 is easier to load cleanly than 35mm. The spacing is wider, so it's easier to feel if something is wrong, and you don't have to back up as far to fix it.
In switching from an el-cheapo no-name 120 reel to Hewes, I didn't experience huge changes in loading ease, *except* with Tri-X. I'm not sure if the strip is minutely wider than the other films I work with, or if there's something slightly different about the way the base flexes when handled, or what, but my batting average on loading Tri-X on the cheap reel was well below the Mendoza line. I don't think I've ever had a loading glitch with the Hewes reel.