I think the Davide and mini davide are slightly superior to the pro tank when it comes to gurgle/leak when less than half full. On the other hand the kangers are easier to fill. The minidavide is especially annoying to fill from a bottle, the holes in the baffle are pretty small.
But that baffle is probably what makes them leak less when low... you can vape a Davide all the way to empty usually.
I have both the Davide, and Pro Tank II, and find that my Davide leaks when laid in it's side. The Kanger has never leaked. Both are great vaping, but because of the leaking, I use the Kanger more. Actually, my second one arrived today, just waiting on my juice to get here to fill it!