OP Here with an update –

Appreciate all the info!

I booked the tickets on my Costco Visa. I got the MQD’s I wanted from the Reserve card & won’t be able to hit the next tier. So back to the Costco Visa.

lindros2 – I am Elite so already get free bags. The Reserve card being linked to my profile gets me an extra bag regardless of how the flight is paid for.

ATOBTTR – Interesting comparison & hadn’t thought of that. I do like the flexibility of the Costco Visa. Basically get cash with the rebate voucher to spend on whatever.

I did access a Centurion lounge when on a Delta ticket booked using miles. i.e., the ticket wasn’t charged to the card (except for the fee). On this trip, I’ll be with my wife & 2 adult kids so don’t believe I can get me + 3 others free access into the Delta / Centurion lounges anyhow.