It all boils down to compromises. A full size half wave dipole is a standard everyone can relate to performance wise. If you only have room for a 40m dipole at about 63ft and you want to operate on 80m that needs 133ft but you don't have that much space, you have to compromise and that can go many different directions with many levels of (poor) performance.
The resonant End Fed Half Wave will be a half wavelength long on the lowest band its designed for, so a 40 through 10m version will be about 63ft long. Hang it in the exact same place as a 63ft long center fed 40m dipole and you cannot tell the difference, but the center fed 40m dipole will only work on 40m and maybe 15m where the EFHW will work great on 40, 20, 15 and 10m.
Now compare that to the 9:1 un-un with a non resonant length of wire, but similar in length to a 40m EFHW and you will need a tuner and it might be usable from 80m or even 160m through 10m but with much reduce performance over the resonant EFHW. And you will have potential problems like RF on the coax, because the 9:1 types rely on the coax as a counterpoise and the coax can radiate almost as much as the antenna wire. You must use a good common mode choke with these or you can actually get RF burns of metal parts of the radio or even the microphone. Bottom line here is a 63ft 40-10m EFHW will greatly outperform a 9:1 with 98ft of wire (EASY TENNA) on 40-10m but it won't go below 40m.
Then you have the ZS6BKW, which works different than the two end feds I just mentioned. Since its a center fed dipole and an amount of it is fed with low loss balanced line, it can cheat in ways the others can't get away with. Its about 94ft long and will put out a much better signal on 80 through 10m than the 98ft EASY TENNA thing you are considering. And it will probably have a better match on most bands 40 through 10 than the easy thing. 80m on the ZS6BKW will be in the 7:1 VSWR range but it will still perform very well on 80 and leaps and bounds better than the easy thing.
Many of us have experimented with the same antennas you are considering and know how they work and I am trying to get you the best antenna that will fit your space rather than see you end up with a dog of an antenna. And beware of antenna advertisements, their only designed to sell antennas and not necessarily to make good on air contacts.
Well, you have told me things that I have to admit that I have no clue about. I have never heard of an unun until you mentioned it but I looked it up so now I know what it means. As I have said before, I have limited options for mounting a antenna on or near my house due to power lines all around the house. The EFHW antenna seems to be my best option. The "Easy-Tenna" comes in a 10 to 80 meter version as well but about the same length. I have attached a top down (Google Maps) satellite picture of my house. The power lines that did not show up in the picture are marked by yellow lines. The arrow is pointing to the high tension lines across the side road. Take a look at it and let me know if you have any other recommendations. Thanks.