Only things loaded are the App Store, iTunes (with no music loaded yet), Calculator, Messages, Mail, and Safari (no extra tabs). Note the memory usage.
Even though I have an i5/16GB MacBook now, too, and I'm all for it, I think it's safe to caution against reading into the "Memory Used" tab too much.
As stated, MacOS keeps things in memory even after they are closed... and only until another app requires this memory that it's freed up for those apps. Otherwise these things just sit in memory.
You can see this from a quick gander at the "App Memory" + "Wired Memory" + "Compressed" space on the right.
"App Memory" = memory currently in use by apps (whether they are active or not active/already closed down)
"Wired Memory" = persistent memory used all the time by the system
"Compressed" = memory being compressed by the OS because these are things that are not used very often but will still benefit from being in memory rather than having to be read back in from storage.
You kind of have to subtract the total memory usage by active processes in the list of running processes from the "App Memory" amount in order to see how much of "App Memory" is used by inactive/closed down apps. But here's a quick calculation for your current tab:
Total memory usage (from Messages process to CalNCService): 1.50GB
Total app memory usage as reported = 6.32GB
Total memory being used by inactive/closed down processes = 4.82GB
"Real" memory usage = 1.50GB (from active processes) + 2.27GB (wired memory) + 454.3MB = 4.21GB
That's give or take, since I haven't taken into account the rest of the running processes yet. But it's a far cry from the 9GB reported by MacOS.
Or here, let's analyze this on a 8GB MacBook:
With some real processes running. Here's memory usage with Safari (3 tabs) + Firefox (2 tabs) + Microsoft Word (1 document), just the "usual average usage", I guess.
Total active process memory = 2.93GB (oh?)
Total app memory usage as reported = 2.82GB (oh??)
Total memory being used by inactive/closed down processes = 2.82 - 2.93 = -0.11GB (oh???)
Approximate "real" memory usage: 2.93GB (as calculated above) + 1.48GB (wired memory) + 0.29GB (compressed) = 4.7GB
So what's going on here? Why would I have "negative" memory used by inactive/closed down processes? Well, that's because the total active process memory calculation takes into account everything, so it would actually include some "system processes" as well, which are not reported in "app memory" (Apple makes a very clear distinction of this in their documentation). In short, this is because I'm "overestimating" memory usage by the system.
But you can see that the memory usage of a 8GB MacBook with browsers and Word running is actually not much more than your MacBook with 16GB of RAM. Even with overestimation of system process memory use.
And that's normal, because if more memory is needed, MacOS doesn't try to compress that memory or use swap, but instead, it would purge some of the processes that are active but not in use, until those processes are needed again. This is the better solution than compressing (takes time also to decompress) and using swap (page file/virtual memory).
On a MacBook with 16GB, the OS just goes to town and leaves everything in memory indefinitely. Considering the "negative" range of inactive app/process memory usage I calculated above is in the 100MB, I'd say 8GB is "just about enough" for MacOS right now. Whereas 16GB is just too abundant (evident by a whopping 4.82GB reported by the OS that's not in use by the processes). Launching and resuming apps should probably be much faster with 16GB RAM too, as can be seen by how much memory is still in use by apps that are not open. But then, it's not like you're missing out on much with 8GB of RAM. If nothing else, the 16GB memory looks like it'll always be in use (due to the way the OS works, as detailed above), and that means a 16GB MacBook will always draw that much more power from the battery compared to a 8GB MacBook. 8GB should be better for power consumption. (and by the way, I think this gives a hint into why Apple is reluctant to include more RAM - 32GB - with the MacBook Pro, too, as all of the RAM will be in use all the time with this mechanism)
This also should show that for most users, 8GB should be enough. With some tabs in Safari + Word, there's still enough memory for other things before swap is engaged. 16GB is just too plentiful. I don't think you'll run into swap with 16GB at all unless you do data analysis, but in which case, you would not look at the MacBook to purchase in the first place.
And that's that! I went 16GB, too, knowing full well its benefits and drawbacks, but then for the occasion that I need that much memory, the 8GB MacBook will feel a bit cramped.
^ also this is to debunk those trying to say "oh, MacOS is such a memory hog!". It's not. MacOS just adapts and optimizes its operations based on how much resource is available. I think that's very clever. Windows and Linux should learn from this.
