in any real-world choice scenario, it's pretty much always better to take 2x slower RAM than 1x of much faster RAM
I'm not sure I agree with this. RAM is so damn cheap these days that you can easily afford more than you can actually used.
I have machines at work and home equipped with 16 GB of RAM, and that tends to work out to 4 GB of useful RAM, and 12 GB of dubiously helpful disk cache...
My main point is that the faster RAM will make literally no difference in your workflow -- It barely shows up in benchmarks that simulate workflows (2-5%) maybe -- and that's without the human factor, wherein every sip of coffee you take is on the same order of time as the difference the faster RAM will make on a job that takes a handful of minutes to process. The only caveat is if you're sharing your RAM with a modernish integrated GPU (like a Haswell CPU or AMD APU), then it can make a measurable difference to gaming or multimedia. Otherwise, faster RAM is only of use to overclockers.
My experience with RAM usage is quite different (its bound to be) -- My work machine has 12 gigs, and if I have one or two spartan VMs running on 3GB each, the 6-9 GB that's left over is actually quite painful to deal with. I pretty commonly have Visual Studio, MSWord, Outlook, and 1-2 dozen chrome tabs open (Chrome is a pig, frankly), alongside at least 1 VM, and Windows usually informs me that I should close some programs because I'm running low on memory at least daily.
In my experience, more RAM is the single best investment you can make in your computers performance up to 12-16GB (at that point, get a good SSD if you don't yet have one). 8GB is a practical minimum today, 16 is better. If you run VMs, add 4GB for each one you might need to run concurrently. My laptop actually has 32GB because I sometimes am dedicating half of that to VMs.
Anyhow, I wasn't really suggesting OP should go crazy and get 32gigs of RAM -- 8 is workable, 16 is more than enough, and future-proof for most. I was just saying don't go out and spend 2x as much getting the fastest 8 or 16GB you can find, because there's precious little difference between that and stuff that runs at slightly more pedestrian speeds. I'd rather not spend the money on negligible performance, and get 16GB instead of 8GB, put that money into other components, or pocket it.
I'm also not advocating for getting the cheapest RAM one can find. In my experience, inexpensive RAM has been the source of more of my hardware troubles than any other component. There's plenty of cheap, poor-quality RAM in the market, and there's also some less-expensive "performance" RAM that's actually just standard-grade RAM configured to tell your motherboard to clock it higher and feed it higher voltage (a factory-overclock basically, rather than actually being a more-capable part to begin with). The last three times I've purchased RAM, I've bought G.Skill and haven't had any problems -- I have had problems with Kingmax and Crucial -- RAM seems to have come back up a bit in price since a year ago when I bought my laptop, but back then I paid just a little over $200 for 4x8GB DDR3 SO-DIMMs that were actually quite fast still, but there were still higher-speed, lower-latency kits by G.Skill and others that were running $250+ for 2x8GB.
