Welcome to OG.
The Mexican Death Sativa is a cross made by Jim Ortega (maybe you’ve heard of the Ortega Indica strain? Same dude, even if Google tells you that it was bred by Mr. Nice seeds or whoever). Apparently, he took all of his favorite Mexican strains and created the Mexican Death Sativa. Kind of a similar breeding process as Haze, except the genetics are all Mexican. I’ve read that there are different phenotypes (not surprising), but that the Guerrero phenotype is a popular and sought-after one. I have no idea what a Guerrero phenotype looks like, but that’s the one that Kiona etc have been raving about on IG. I’ve got two of the Mexican Melon (MDS x Dragon Energy) females in veg now, gonna flip on July 1. One of them is growing strangely, but in a good way. She’s throwing branches really randomly, one branch will grow to the right, then, a half-inch above, another branch will grow at a like 100 degree angle from the branch below… Never seen anything like it.
As far as the Vietnam Black, I don’t know much about it, but I did get some of the #164 as freebies from Doc a while back. No plans to run them any time soon. I sometimes suffer from panic attacks and from everything I’ve read about Vietnam Black, it doesn’t sound like a strain that somebody who’s dealing with panic attacks should blaze haha…
Anyway, hope that helps.