To quantify this, we're talking read speeds of around 950 vs 850 MB/s and write speeds of around 740 vs 450 MB/s in comparing the 2016 to 2015. So a modest gain in read speeds and a pretty good bump in write speeds.
https://www.macrumors.com/2016/04/25/2016-macbook-review-roundup/
Which scenarios are you thinking of where this makes enough difference to note?
I'm not coming up with everyday scenarious where this would noticeably impact the user. This is why I'm asking.
It seems you have to be reading/writing multi-gigabyte files to even notice a difference. Further, it seems to me that in most such scenarios you're applying some sort of processing to the files and I'd think other factors (CPU/memory/network) would be the limiting factor before the SSD.
Your thoughts?
About the write-times: I think that only will be noticeable when writing a lot of data, like transfering your iTunes library from an other mac, installing an OS update, etc. Even if the there will be written a lot to the SSD while running your system, I think that there will be no significant slowdown in every day usage. A lot of little files will be written fast enough to be fine for daly usage. IMHO.
Read-times: That comes in handy when you boot up your system or start an app for the first time. Starting an app for a second time - without rebooting the system - would be fast because of the memory management of OS X. If you have a look at the activity monitor, memory, you will notice a large block called "inactive" (I think meanwhile they renamed it to "files in cache"). When you close your app, the executable part and some kind of internal data (like icons, windows of the app, etc) will stay in memory as long as that memory won't be used by an other app. When you start the app again, that part cached in memory will be used. Because of this starting an app a second time is much faster. (If they changed that mechanism in one of the last OS updates, please tell me).
Well, will you notice a difference in your daily needs? I don't think so. Maybe you will notice a difference if you directly compare the two models or if you are alrady comfortable with something faster than the 2015 models read / write speed. If you are comming from a normal HDD or a slower SSD, you will be blown away from the SSD speed, anyway (the first months with my 2013 MBA that had an PCI Express SSD for the first time, I was so exited how fast that system boots up and loads apps compared to my 2011 MBP with an upgraded SATA SSD!).
While using your system, you will start an app and save your files. And I have the strong feeling, that you won't sit with a stopwatch in front of your computer to stop the time it needs for that tasks.
So if the overall performance and the battery life of the 2015 Modell is fine for you, you can save money and use it for other usefull stuff like adapters, iTunes content, pay for a candle light dinner with someone special - which could have more long-time value than buying a Macbook, at least I hope that for you. And btw, let your Macbook at home for that time...