Arm triangles are gay because they are impure. I swear I talked about this even before I absented myself for 5 years.
Look, there's only three chokes that matter for real fighting: rear naked choke, guillotine, and north south choke. Everything else is, at best, a gamble. Any choke which: (i) involves clothing; (ii) allows for an arm--or anything else--inside; or (iii) can only be done from the bottom is bogus. In a real fight, when people don't care about rules or safety or no slams or any such bullshit, you want chokes that let you have "pure" access to the neck. This is the origin of the old school phrase when it's giddy up time, "Go for the throat."
You did say this years ago. Apparently, Marcelo Garcia has a similar view.
But I've seen too many contests (UFC and elsewhere) ended by Arm Triangle to agree. Seems to me, even if your Arm Triangle is ineffective, you sacrifice little in control/position; but I suspect that a sunk Arm Triangle will usually work. Especially on the street, where your opponent is unlikely to be a student of the art.