I can't speak to any of those that Amazon sells... But I can tell you that I love the Thermoworks Thermopop... I got one on sale a few years back, for like $25. I liked it so much, the next time I saw a sale, I bought two more. I love having 3 of them, (together they were about the same price as a MK4 on sale) because I am somewhat forgetful, and tend to occasionally misplace things. So far I haven't misplaced all three at once.
My wife, who's not much of a cook, is now regularly using the Thermopop to check to make sure stuff she cooks is actually done... that in itself , is in my mind proof that they are about as great as you can get from a relatively cheap instant read thermometer.
Waterproof.... I dropped one last winter out in the snow... didn't find it for 2 months, still worked when I found it.
No complaints at all about the Thermopop, nothing but high praise for them, especially if you can get one on sale.