Where I stand on loops:
Based on design work and in use. Loop antennas are useful either in the
wide band receiving only type or tuned transmitting type. They are not
close to full size dipoles in performance never minding beams. However
they are self contained, compact, have a pair of very deep directional nulls.
Those features often offset the low gain and touchy tuning and on the
low bands like 80 and 160 they can be very useful even RX only for beating
local noise issues. Often that is more important then how big your signal is.
As such Loops along with dipoles and other well understood antennas be part
of the hams box of tricks to enable communications.
Bob/N4FBZ nails it:
"The thing is, every ham lives in a different situation... different factors that will strongly affect the performance of their antennas.
To that I'll add my three rules for antennas:***If you want a better antenna add more metal (more elements
***If you want to improve any antenna raise it higher.
or longer wire and so on) as bigger is often better.
***Above all else put something up or toss a wire out the window
on the ground floor, it will be better than a bucket of wire in the shed.
And you will then have an antenna you can compare you future work to.