All good points.
But a "cheapo" octo may actually be quite a good reg. For instance, I knew one shop selling super-cheap octos and they turned out to be made by Kirby-Morgan (fantastic stuff) and worked better than many primaries.
Spectre, you are a bit of an exception...Apeks regs are a bit overpressurized, and making a Mares octo (built for very low IP's and with a large orifice) work with them require a LOT of detuning. Apeks with Apeks, I allus say.
All that said, I recommend avid divers to keep a slightly (notice I say slightly) detuned primary as an octopus. That is, in fact, what many octos amount to. USD octos have a tougher spring. R190's use a plastic orifice. Apeks octos lack spring adjustments.
It is true that the "flat" style of octo's (such as the USD LPO and the Sherwood Silhouette Octo) breathe like dogs. An unfortunate combination of short lever, strong spring, and small diaphragm.
But they are reliable, which is why you find them on so much rental gear.
The best option is to buy two *adjustable* primaries...and then keep the one on a longer hose detuned for your buddy. This is of course, if you are diving standard recreational configuration. I would recommend very different equipment for technical or DIR divers, who are a large part of my clientele.
Another reason octos sometimes seem to be "worse" than primaries is because there is no venturi channel on the octopus ports of most diaphragm regulators.
Just my twenty cents.
C