I have a now dated Lenovo y510p that work supplied. It has an older i7 than your new models listed, 16GB RAM and some 750m GPU. It runs my stuff fine. The ONE thing the office did last week was to swap in a SSD. Now it feel current.

Let me share how I compare CPUs. I use CPUBOSS.

And 16GB did not eliminate lags. I think it may even induce lag as cache flushing takes longer as there is more to flush.

What really helped was the SSD as to overall performance on the y510p.

-> As to the SSD dying, it looks like the deaths will be same as or lower than run of the mill HDDs.

MSI shouldn't have much to say as a lot of what you asked is comparing apples to apples. Or picking the winner in a horse race. It's a photo finish.

---> Google this to compare notebook GPUS.

Notebookcheck 960m
(same) 970m