The M.2 form factor still has a key advantage in that it is compact and avoids running power and SATA cables which you'd have to do for a "normal" SSD.

But if your motherboard already comes with its own M.2 SSD cooling kit, save yourself the cash and skip the heatsink. If more storage on the cheap is what you're looking for, and let's face it ...

As for one type of SSD vs another, probably like the RAM. I have a PCIe 4x SSD (WD_BLACK 500GB SN770), an M2 SATA one (an older Samsung), and a SATA one (Crucial).

Hardware Storage SSDs Samsung's just started producing what is effectively its first proper PCIe 5.0 SSD and it's faster than any currently on the market ...

Benchmark testing has indicated that the 256GB variant of the 13-inch MacBook Pro with M2 chip offers slower SSD performance than its M1 equivalent, and now real-world stress testing by YouTuber ...