The only reason I own ET-C over D is the earlier reset. Less risk to reward. That's it. It's likely, but not a slam dunk, that D's yield will be higher when it resets. However the longer you hold a floating rate preferred the more influence the Fed has on your investment returns. ET-C is a play on a higher likelihood of a known Fed funds rate due to an earlier reset.
If the labor market softens and the Fed pauses investors will be rethinking the timeframe of their floating rate preferreds reset and what 3 month LIBOR (or SOFR) will look like at that time. I would not want to be heavy into a floating rate preferred portfolio if the topic of the Fed cutting rates gains traction. Due to an Investor sentiment change. That's why most of my preferreds are fixed. As soon as the Fed pauses my fixed preferreds will catch a bid as investors will look at locking in a fixed yield as the more attractive and safer investment.
Again I'm looking at ET-C as a short term trade only.