I saw the tour as well.
You're Stingingly clear bias shows through in your post.
GnR were definitely the bigger draw in 1992.
Not in the United States. Both bands had been on tour for a year prior to the start of the co-headlining stadium tour.
Number of Arena shows by each band in the United States prior to the start of their co-headlining tour in July 1992:
Metallica: 127 U.S. arena shows from October 12, 1991 through July 5, 1991.
Guns N Roses: 61 U.S. arena shows from May 24, 1991 through April 9, 1992
You can then break it down by city and you'll see Metallica for the most part playing just as many arena shows if not more than Guns N Roses per city. In addition, Metallica was doing 360 degree arena shows with seating behind the stage. Guns N Roses did not use seats behind the stage in their arena shows.
Definitely the bigger draw? The results of their touring prior to July 1992 in the United States don't show that. Also remember that prior to 1991, Guns N Roses had only been a support act for other artist when it came to Arena or Stadium shows in the United States. Metallica on the other hand had already done a their own 100 date plus arena tour in the United States back in 1988/1989 in support of the "And Justice For All" album.