You're kind of all over the place here, so I'll break things down a bit:
1) 1600 MHz RAM works fine in the 2011 MacBook Pro, but it provides no tangible benefit for everyday use. I said this in my initial reply to you.
2) RAM is RAM, at least in the vast majority of cases. Modern Macs, 2011 vintage and onward, are not nearly as picky about memory as they have been in the past. I've tested ADATA, G.Skill, Crucial, Samsung, and others, including 1333 and 1600 MHz, and with one or two exceptions, all have worked just fine, passing memory test software run over the course of 12 continuous hours.
3) The whole idea of faster speeds resulting in instability is probably true when a new RAM specification comes out, for example when 1600 MHz modules started appearing. As time goes on and production practices mature, this becomes less and less of a problem. I would consider it a non-issue at this point.
4) Latency. Like the actual speed of the memory, you won't see any noticeable difference in everyday use.
As for exactly what you should buy, I've had the best luck with Crucial and G.Skill memory. I'm currently running 16 GB of Crucial 1333 MHz because 1) I was lucky enough to pick it up on sale for a very cheap price and 2) it runs at a lower voltage than most other RAM (1.35v vs 1.5 v).
I'm not going to make any sort of claim that having the lower voltage memory has made a difference to my battery life or anything like that. However, if there's any way I can save a bit of power some place, I'm going to take advantage of it. The quad-core i7 CPU and AMD Radeon GPU in the MacBook Pro can be power hogs. Get the system going hard enough, and the standard 85W AC adapter will start working as hard as it possibly can. If Razer, a much smaller company, can design a slim-line (and very attractive looking I might add) 120W AC adapter for its Blade notebook, surely a corporation with billions in cash in the bank can do the same for its products.