Hi,

I run a non-resonate end fed antenna because it offers a reasonable tradeoff between efficiency and the space needed to string it up on my property. I only need about 55' to cover down to 80 meters. 

The antenna in not a random length. It is a specially calculated length to provide as close as possible to the correct impedance, into the 9:1 unun transformer for the bands you want to operate on. 

Not much different the efficiency tradeoff people make using shortened verticals with all sorts of rods, spikes, spiders, coils and whatnot gizmos to make them "resonate".

But if you have more room, the bigger the better seems to apply. 

Here is a presentation regarding end-fed non-resonate antennas.

https://palomar-engineers.com/wp-content/uploads/End-Fed-Antenna-Secrets-YUMA-2020-Hamfest.pdf

Tom, wb6b