Would I see a noticeable difference in performance with an M.2 SSD?

Jan 20, 2019
I realise that this question has been asked many times before, but I'm asking now in 2019 in case there's been any major changes in SSD performance or use over the last couple years and also particular to my own circumstances so forgive me if I'm being repetitive.

I'm thinking of buying an M.2 SSD - probably a Samsung 960 Evo 500GB. My current SSD, which is performing fine but just getting a bit full, is a PNY CS900 250GB.

Nothing fancy admittedly but I've already removed as much as I am comfortable with from the main drive and transferred it to my data drive (a 1TB mechanical hard drive which I'm going to change to a 4TB drive soon). I've also utilised my backup 3TB drive and 3TB personal cloud device, as well as cloud storage to limit the amount of used space.

Startup time is already pretty quick, I guess around 15 seconds from switch on to settled desktop, and the only things that drag it a little are scheduled tasks such as opening Speedfan, Evernote and MSI Afterburner. I could probably shave a few more seconds off that if I got rid.

I am very impulsive when it comes to buying tech though, and I wonder if I'd really see a difference? I don't do any heavy write based tasks such as image or video editing or downloading vast loads of data other than game updates, which generally go to my data disk anyway. The SSD is my OS disc and the only large application on there is World of Warcraft which, if I bought a new and fast HDD would probably be transferred across. My games aren't the type which really benefit from fast SSD access and, other than initial loading time, don't take much resources from storage.

Average use is browsing the web, watching youtube, office tasks like word or excel, the most intensive games I play are WoW on full settings, MoH 2010, Space Hulk: Deathwing and that's pretty much it. My system is hugely overpowered for what I do, so maybe I'm just being materialistic and need to grow up (GPU and CPU with water cooling and they never get hot and games run slick at around 110FPS on full settings.)

Which leads me to another sub-question - with an M.2 being fitted on an Asus Z97 Pro-Gamer, so I need a heatsink on aforementioned SSD? I have water cooled CPU and three case fans all operating from Speedfan and the system is rarely hot as I've already said, but SSDs are different from CPU and GPU task which I guess are much more read than write based.

If I'm just being silly, be blunt, I probably need to put a padlock on my wallet. I think a replacement data disk would be wise but I'm questioning the need for an M.2 and need someone to act as my conscience :)
There are two types of M.2: SATA and NVMe.
There might be no performance differences between a M.2 SATA SSD and the PNY CS900 2.5” SSD SATA III disk.

You could get a little bit of speed with a M.2 NVMe disk.You might see 1 to 3 seconds max on a NVME SSD disk compared to a SATA III SSD when opening large files or loading a game.
Booting time might improve half to 1 second faster.
FPS is not usually affected since games are running from RAM.
Take in consideration those numbers and see if they are enough of a noticeable difference in performance for you.