Difference between rolls wouldn't work because a person could roll a 1 with -1 Strength and no Athletics while the other rolls 20 with +5 Athletics, thus throwing them 25 feet, or something similar. On the other hand, a Strength 10 person could wind up shoving an ogre 15 feet just because the ogre rolled a 1.
+1, that would look ridiculous. Almost too much larfun, even for Larian.
Rolls should determine who wins the Athletics contest. The distance should be determined by Athletics (STR modifier + Athletics proficiency / expertise, if any), and maybe size category difference (say, +5 feet per unit of difference). Even Lae'zel with STR 18 can't really shove an ogre much, if at all. However she should have a much better chance sending a halfling or a goblin flying (not far, and it has to be a very low altitude flight, but still).
