What's the difference between the Pro V1 and Pro V1x?

Across reviewers we read, the Pro V1x flies higher, spins more, and feels firmer than the Pro V1. Specialist community threads and mygolfspy.com generally fit more golfers into the V1x for added iron spin and trajectory, while the Pro V1 is preferred by players who want a slightly softer feel and a more penetrating ball flight.