If you are cruising at 20 mph or more most of the time aero is probably going to pay off .... and if weight is a big issue, go weight-weenie on other parts of the build.
I am not an engineer, and I know I will probably, by saying those words, summon the demon-souls of every pro and amateur scientist in the universe .... but I doubt you are going to notice a huge difference in measured performance no matter which way you go.
The pros use everything they have to get every advantage---because they have maxed out the engine already, and because a one-percent edge might be a win or a loss. To an amateur rider, one percent will get lost in the weeds ... did you have a stressful day at work, eat some too-greasy/too-spicy Thai or Mexican for lunch, did you get good sleep, are you just not really feeling it but would rather ride the bike than the couch ......
I have a couple main rides right now---both endurance frames---but one is about 18 pounds with lights, tools, tubes, and food, while the other is about 28 ready to roll. I don't see anything like a one-third increase in performance despite the increase in weight .... in fact, on any given couple of days, even riding the exact same routes, my performance is almost always governed by my attitude that day. I am sure if I swapped every other day and times everything to precision and rode exactly identical routes .... I might find a tiny tilt toward the lighter bike over time .... it just makes sense. But even on hilly rides, how my legs and lungs and heart feel is what determines how hard I hit the hills--or how hard the hills hit me. The bike weight doesn't seem to be the determining factor.
Buy the bike you like better, I'd say. Also comfort is a much bigger deal (IMO) for non-pro riders .... if the bike hits hard on bumps or the riding position is a little too extreme for some days, you are a lot more likely not to enjoy the ride as much (possibly) and a lot less likely to hit it as hard (possibly.)
Another thing .... likely the biggest drag on the bike is the rider. if you ride in full aero position 100 percent of the time, then sure .... get aero socks and aero gloves and an aero frame. But if you sit up even a little, that one-percent aero advantage is completely nullified. Like those old-school long-tail TT helmets .... lean a few degrees forward and the aero tail becomes an aero-sail, an air-brake.
Buy the bike which you like better .... color or style, or if you really think aero is important, buy the more aero bike. Likely the on-road experience with either of the bikes you mention will be close enough that what will determine the experience and the performance, will be all mental---if you feel fast, or just like riding the bike .... It will be the faster of the two.