Okay, I promised to update this thread after my family traveled, so here is what they experienced.

Very short answer, where both nonstop flights are available:
Delta First Class was superior to JetBlue Even More Space (booking an entire row of three seats for two travelers), and it was "worth at least a couple of hundred more dollars" (per ticket) for the former, though not necessarily worth paying twice as much (or more.)

The travelers in this case were two people who haven't flown since the pandemic started, though both were occasional- to semi-regular international travelers years ago. One is elderly and has multiple health issues. Only one has Global Entry, so neither used express lanes based on that status during the trip (i.e., they stayed together at all times during travel.) Neither drinks alcohol, so that aspect of catering was irrelevant to their happiness. Rather than luxury, saving time and being less physically stressed was the most important reason for upgrading from standard Economy on this trip.

Almost as important as flight selection, according to my family, was the great value in paying for VIP departure service at AUA ($190 pp from First Class Experience Aruba) when leaving the country. Standing outdoors in the sun would have been necessary without this "fast track" service, and my relatives did *not* leave on the busiest day of the week. Even with VIP service to ease the way, my family found the Aruba airport pretty aggravating and they are unsure whether they will visit again with the family members who go there annually.

Delta First Class Boston to Aruba
Delta offered the earlier departure out of Boston for AUA, and that was yet another reason--in addition to availability of a less dense First Class cabin--we chose this particular outgoing flight. The earlier flight meant landing at AUA during a somewhat less peak hour, with only one international flight processing at a time instead of several. Overall, arrival in Aruba was pretty standard, and not stressful to these travelers, contrary to their departure experience.

Arriving at Logan airport a full three hours ahead (standard international flight recommendation) wasn't necessary, either, with no bags to check and priority security access due to ticketed cabin class. They got to BOS roughly two hours before their 06:45 flight and still had about an hour to enjoy the Delta SkyClub before their flight. Access to SkyClub was via AmEx Platinum card since, in the mind-bending logic of an airline, "International travel excludes customers traveling to/from the Caribbean." The lounge didn't wow them, but they ranked it “pretty good," and neither felt it was too crowded. (The airport itself did feel crowded to these two who have both been working from home since 2020.) They appreciated getting something to eat before takeoff, because the meal on a Delta F flight to Aruba is a sad little boxed thing. My family thanked me for warning them ahead of time about what they should expect; this would have been an unpleasant surprise to them otherwise.

Before boarding in Boston, at the gate, my spouse felt it was quite effortful to convince agents there that they belonged in the first class line. He mentioned needing to show his boarding pass more than once before boarding as agents kept trying to herd them toward the Economy queue. Again, as rare flyers these days, they probably didn’t have the body language of elite road warriors, and they were definitely dressed down on their way to the beach, but I consider this a failure at the gate. Passengers should be given a chance to show their boarding passes instead of being judged by their looks/a foreign accent.Arrival in Aruba was easy and uneventful. We’d considered booking VIP arrival service, but ended up glad we skipped that expense. It was the right call for arrival ONLY; not departure. The rest of the family members who’d flown in with JetBlue one day before experienced a much less smooth arrival, probably due to time of day and number of incoming planes at one time. Picking a flight leaving a couple of hours earlier was the right decision for AUA.

Because I asked specifically, my husband did notice, and report back to me, that they were offered a pre-departure beverage out of Boston, though he didn't feel comfortable taking off his mask before the ventilation system was running in full gear to partake of one. He also complained that the power jack at his seat was loose and his Apple brick kept falling out during the flight.