I've been using magnetic loops for 20 years
A magnetic loop can work well if it has two qualities: enough power handling (a 5 kV vacuum variable will handle 100 Watts, 15kV will do a kW); and a decent remote tuning setup. tuning is critical, as Eham reviews show the main dfficulty is getting the SWR properly dipped. Thanks to the popularity of robotics, low cost stepper motors are available, and do the job.
While size isn't critical, efficiency goes rapidly downhill at diameters less than than about a 20th of a wavelength. 1/2" or 3/4" copper tubing is self supporting, low loss, and is easily flattened and drilled for low loss connections. Paint it a dark color for stealth, and to avoid corrosion.
Dealing with high voltages and extreme narrow bandwidth are the price paid for an antenna that makes a magnetic near field, which seems to penetrate nearby conductors, such as trees, the ground, house wiring, powerlines, etc. almost as if they weren't there, because induced currents are in phase with the antenna's field. Near field losses are reduced by an S unit in a typical urban location, when compared with a wire antenna or a vertical whose electrical near field induces out of phase re-radiation.
The statements about quiet receive are approximately correct. In my experience, fixed local terrestrial noise sources (a pole pig with nesting squirrels, an LED streetlight)can be reduced typically by two S units (10 dB) by a vertically hung loop that is tied with a side line to keep the null lined up. Unlike stations using an antenna tuner at the radio, received and transmitted RFI does not come from the loop's feedline because its matched all the way to the antenna, where tuning and matching is done.
Further details are at www.x44.cc, or by googling my ham callsign, K1QAR