I think it can be helpful and educational (and dare I say fun) to sit and have discussions about antennas and the math behind them. However, In some cases like this, I think it is a little like arguing about what sports car is better based on the published specifications when, in fact, the best thing to do is get out and drive.
I would suggest just picking something “good,” get out there, and dont look back for a while. With experience and/or a desire to tinker at a later point, you may try different things, but just picking something and going with it will pay far more educational dividends than constantly changing. In this hobby and many others I have been in, people look for the perfect killer antenna or recipe or whatever. The truth is, it doesnt exist.
I currently use a resonant EFHW with a home built 64:1 unun. In just getting out and using it, I have learned a lot about it and have been doing well with it. Is there something better out there? Maybe. Is there something better out there for me? No, not currenty.
Couldn’t agree more! Any antenna that’s in the air and connected to a radio is infinitely more effective than the best of super-antennas you’re thinking of building
I would like to stress that for a SOTA antenna, theoretical efficiency is only one of the many variables for its actual usefulness and performance. In my SOTA antenna projects, I now tend to start with what is doable from the perspective of handling and then test whether it works sufficiently well. For instance, my two SOTA vertical designs:
are mainly inspired by an optimized handing on small or crowded summits. They are less performant than a full-size dipole (center-fed or endfed), but in practice, I can manage more QSOs on a challenging summit because I am QRV within 1 - 2 minutes. Still, I can work @SP9AMH with QRP2QRP regularly.
A dipole / EFHW with traps might be a little less efficient than a linked dipole. But when in a hurry on a summit, the antenna with traps allows me trying for a nice DX catch on 20m at the end of an activation in winter in a few more minutes, while I would not have the time to take down the antenna for a band-change.
As for the “any antenna design works” argument, I think we should add that this is true as long as you do not make any mistake building and tuning it: If you just look for a low SWR, you may never notice very bad construction mistakes that cause a lot of losses, for instance
long coax for sections with a very different impedance from 50 ohms,
shorts or cold solder joints,
core losses,
capacitative coupling into nearby metal or otherwise conductive objects,
etc.
So a WSPR performance comparison against a reference design is always useful. Low SWR just assures an impedance match to the transceiver, so that the finals do not get blown away. 80 % of your antenna can be actually a dummy load, while you can still achieve a 1:1 SWR, as any full dummy loads proves.
If you add two pairs of the SOTAbeams Pico Traps to your 40m center-fed dipole, you will be able to turn it into a very convenient 3-band antenna that does not require an ATU either.
See here:
You will only have to observe that
you have to tune it starting with the highest frequency and the traps and following wire segments already installed and
the resonant lengths will be a bit shorter than for a linked dipole because the inductances of the traps extend the respective segment electrically.