Varsho is almost a lock to produce a higher WAR total compared to Kiermaier if he plays an entire season in center field. He's basically averaged 4 wins per season in his time in center field over his career and he's most likely a better center field defender than Kiermaier is at this stage of his career. He's a better baserunner as well, has a much better offensive projection than Kiermaier (106 wRC+ for Varsho vs 88 wRC+ for Kiermaier), is younger/doesn't miss time due to injury, and will be less expensive to boot.
Literally the only thing that was better about Kiermaier vs Varsho last season was the results with the bat, but dig a little deeper and you see the two players produced nearly identical expected statistics, with Varsho coming in a little higher with a .303 xWOBA vs Kiermaier at .301 xWOBA.