I only tried salvadorian tamales once but the place was authentic, they were nasty as fuck all mushy and shit, you'll not a coward cause if you think they're better then mexican ones your smoking crack.
They are better, like a lot. I've had them homemade for years from one of my best friends mom, and a few other times from different people that made them, and they are way better. And trust me I've had homemade Mexican tamales probably more so than those even, and from quite a few different families, and I love them as well, but Salvi ones kill them.
You had them from one place, once, so I don't know if your opinion is valid. Sorry you had shitty ones at some random spot your first go round.