I generally agree with @JustinThyme, I notice substantial overall performance improvement on PCIe/M.2/NVMe SSD vs SATA SSD. Substantial enough that I find myself frustrated when using lowly SATA SSD systems.
Yes, benchmark scores don't always translate into meaningful "real world" performances.
But "real" performance does vary a lot, depending on exactly what is meant by "day-to-day use".
I use a PCIe2 SSD as system drive and RAID-SATA SSD as primary storage on my home hardware because the PCIe bus is saturated. It's by far the "fastest" possible configuration for my particular storage needs that I could install (within budget) on my base platform. But for most people an M.2/NVMe (or RAID-M.2) would be much faster. There are even special-case situations where Intel Optane is dominantly the fastest "day-to-day" performer, even though it's stupidly suboptimal (and stupidly overpriced) for most "real world" users.
To be realistic, you've got a G751JY laptop (HM87, i7-4860HQ, DDR3L, 4GB GTX980M, 1920x1080 display, Gigabit LAN) ... you're not going to be streaming 4K video, crunching hard in multiple VMs, running two dozen apps at a time ... in fact, you lack enough PCIe and DMI lanes between PCH and CPU to even carry maximal SSD bandwidths ... a high-end SATA SSD will suffice. The system might not be quite as snappy and responsive with SATA SSD but it'll definitely be an upgrade from the rust drive you've got spinning now. HDD to SSD is a singularly spectacular performance increase; SSD to PCIe/M.2/NVMe is still a performance increase but not as impressive, "normal people"
* don't consistently make full use of the impressive performance specs in their "day-to-day" use anyhow.
* ROG folks being "abnormal people" in this context - gamers, power users, enthusiasts, overclockers, etc - nothing less than maximum possible performance will do!
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