I prefer dextrose.
When waxy first appeared and was making a big splash, I asked someone I knew at Costello if ABB or ON planned on releasing a version. He replied not at that time, but also told me of a study they conducted comparing a leading WM product to plain old Argo corn starch. I forget all of the criteria, but the corn starch rated higher.
I used corn starch as a training carb for about a year or so, but I seemed to have developed an allergy to it, so I stopped. Honestly, I was probably drinking too much. The pumps were strong on it and my muscles had good fullness, but my gut couldn't take it anymore. I haven't used it since, and I've never tried any of the supplement versions, either.