Hi Justin,
When I first bought my VX, I changed the transmission fluids out with Mobile 1 synthetic transmission fluid. I didn't have the tools to change the gaskets and the filter so I just changed the oil. A year later I tackled that project again and replaced both gaskets and the main pan filter. Because the fluid was relatively new I drained it and reused some of it, but I filled it back up with an O'reilly brand full synthetic (dextron 5 or 3?, the GM kind). It may have been valvoline, but it was much cheaper than the mobile 1. My shift quality was good when I first changed the fluids, but it did get smoother after I changed the filter.

The moral of the story is that I personally do not feel it really matters, aslong as you use the GM required fluid. If you're like most of us here, and have a VX with >100K miles, then you have similar gunk and deposits inside - so just buying the most expensive fluid (mobile 1) won't really undo any of the wear to the transmission. I would not have dropped the $100 on the mobile 1 fluid.