W-4 extra withholding opinions - on the steady check vs the variable check
About to revisit W-4s. We (spouse and I, MFJ) try to target a $500-$1000 refund because we'd psychologically rather get a small refund than write a check. Gross expected around $220K, single job each for both me and my spouse. We were roughly equal last year. My paycheck is always the same, while their paycheck can vary significantly with differentials, extra shift incentives, etc. (Their PTO-only check is less than half of their normal non-incentive check due to differentials.)
For the past several years, the extra withholding has been applied to the variable check because it felt right intuitively. While it has worked fairly well, last year we received a refund nearly triple our target (thus why we are recalculating). I'm just looking for opinions and perhaps pros/cons on whether we should continue with the extra withholding on their variable paycheck or put it on my steady paycheck.