i have never tried 073 but from what i've read it seems to just be a milder version of 018 (less potent but similar body/head high ratios?)
i would say that 018 has more of the 'medicinal' qualities of cannabinoid agonists, including analgesia, drowsiness, munchies, etc (all the things that THC is being used for in cancer/pain patients)... all of these things I feel are heavily 'indica'-focused
while 081 feels more euphoric, speedy, heady high like a sativa-dominant strain. hence they combine nicely to form a well-rounded cannabis replacement.
both cause significant red-eye and cotton mouth, and both still have potential to cause anxiety in acute overdose (vaporizing 5mg to a non-tolerant person)
i feel that the ratio of side-effects to positive effects is very poor with vaporization. Before I start feeling high at all, i notice that my eyes are burning red. On the other hand, oral administration is very smooth. One hour after consumption, the euphoria and body buzz begin to creep in with only slight hints of cotton mouth.
Also, the one thing that makes me REALLY want to smoke real aromatic trees is the act of chasing JWH on tinfoil. It just feels wrong and tastes like shit and i want to clean my mouth out with some sweet sweet herb. When eating a JWH brownie on the other hand, I can get a high that feels remarkably similar to good weed brownie without the psychological temptation of smoking (compulsive redosing)
I am also very curious about 019. Since 073 is butyl, 018 is pentyl, and 019 is hexyl, will the potency of 019 be drastically higher than 018 (as seen in the 073 -> 018 comparison) or drastically reduced? (as seen in the MBDB -> Methyl-K comparison from pihkal). What about the heptyl homologue? What about the 081 (methoxylated napthyl) analog of the hexyl compound? So many flavors, so little time!