Right now the Big 12 payouts are higher largely because they played in the COVID year (probably hopefully not an issue that rears its head again anytime soon) and because they do sell their Tier 3 rights instead of investing them back into the PAC12 network (which is estimated at approximately $250M in value, or $25M/team)

Looking at longer term, it becomes really difficult to clearly say which one will be above.

Here's what we do know (with sources on where it's been reported):

1. The current PAC12 TV deal (beginning in 2012 and going through 2024) is worth $21M/school/yr*
2. That's more than the current Big 12 deal (beginning in 2012 and going through 2025) which is worth $20M/school/yr for the same Tier 1/2 rights (initially $17M/school/yr, but ESPN kept the payout the same after A&M and Mizzou left in an effort to keep Texas from leaving to a conference they didn't control)*
3. Since that time, both conferences have lost important members (Texas A&M, Mizzou, Texas and Oklahoma from the Big 12; USC and UCLA from the PAC12)
4. The estimate I've most commonly seen** for the change in value in the PAC12 next contract is going from $500M/yr ($41.7M/school/yr) to only $300M ($30M/school/yr), which is a large loss (from what it could have been) to be sure, but clearly substantially more than both the PAC12 and Big 12 have been getting.  This would include Tier 1, II and III content ***
5. The PAC12 is currently negotiating their TV deal so has hard numbers on what exactly they would get
6. There is less certainty on what a Big 12 deal would be worth, so estimates range wildly - anywhere from $20M/school/yr**** to $26M/school per school ($22M for Tier 1/2 +$4M/school from ESPN for Tier 3)***** to approximately $45ishM/school/yr****** (though that also assumes a larger CFP with more $ going to each conference, which may not be the case if/when the B1G/SEC break away); also worth noting that other industry insiders have voiced disagreement specifically with that larger prediction*******
7. Analysis******** indicates that the remaining 10 PAC12 teams have a combined 16.7M fans (1.67M/school).  The remaining 12 Big 12 teams have a combined 11.57M fans (964k/school)

Some of that (the Navigate data) does indicate the Big 12 would have a substantial lead, other sources do not.  But there's clearly a lot of uncertainty

* On3 (Current TV deals)
** Canzano (Former Fox exec estimates new PAC12 deal)
*** Mercury News (Previous Estimate of PAC12 deal)
**** TV Rev (estimate of Big 12 deal after OUT and expansion).
***** SicEm 365 (estimate of Big 12 deal after OUT and expansion)
****** Navigate Conference TV Deal Projections (after OUT, but prior to USC/UCLA)
******* CBS Sports (insider disagreement with Navigate)
******** AltimoreCollins (fanbase estimation)