I'm comparing these guys entire careers up to this point. Consider that Varsho's defensive metrics took a dramatic leap forward in the last two seasons, and this will likely play a large part in his future defensive value in the outfield. It seems his first few years in the outfield saw him still getting used to playing the outfield compared to his split catching and outfield duties in his first few seasons. I believe if Varsho would have played full time in center field in 2023 he would have essentially been a 4 win player even with his 2023 offensive numbers, which would have the effect of raising his career average WAR/550 plate appearances to nearly 3.8. This is a much higher quality player than Grisham, who at this point of his career is essentially a 2 win player.
Check out this article to see how Varsho's projections change if it's assumed that he spends all of his time in center field, and not splitting time in left field and center field. This also surmises that his baserunning value doesn't take a dive this early in his career as well, and that he produces similar value on the bases. His Steamer projection would change to over 4 wins in this scenario with this years offensive numbers, and if he produces offense in line with his projections he's suddenly a 5+ win player.
https://bluejaysnation.com/news/a-deep-dive-into-daulton-varshos-value-to-the-blue-jays-moving-forward