The one's from the second site you listed in your post ship from China so they will take an awfully long time to get to you, which also means returns can be quite the hassle getting them back to them if they don't work out. I have bought other items from that site and it has taken between 4-6...
I found a site that sells the nipple drinkers either by themselves in packs of 5 or in pre-made buckets. (something like a 2 quart and a 2 gallon size) So easy to use, fill it, hand it, done. It did take my chickens a little while to get used to but I searched for tips and tricks and they worked...