Remember.... Windows uses Superfetch so your mem usage isn't necessarily X or Y.
As for the SP 2017, I can only compare it to the SP6. I've owned both and, frankly, the SP6 is miles ahead of the 2017 model. If you had a Pro 6, I'd say that you should wait for reviews to see the differences. However, as you have a SP5, the SP7 should offer you a whole heap of performance when compared.
Maybe read the SP6 review to see what you're typically going to get.