Optane 900P vs. 960 EVO NVMe M.2 250GB SSD
https://ark.intel.com/fr...
http://www.samsung.com/fr...
Random reads are significantly lower for the M.2. especially in this capacity range.
The larger M.2. drives get better performance but still fall short of the Optane 900p in every way, performance and reliability.
And since Intel makes the processors, they also optimise the internal bus instructions and transfers. This has the effect of reducing access times in fully virtualised environments.
These are the big differences on the points you can compare.
Knowing your hardware, motherboard, processor, ram is very important when choosing disks if you want full performance optimisation.

Sorry, I didn't understand the question. There is no difference between the Pcie and N.2. version, the components are the same.
The only difference is the connectivity to the motherboard. Which brings you back to the internal bus and priorities.

I bought it and installed it and I'm only talking about feelings, not benchmarks, in terms of difference we must be in the nano range... I'm not sure if it's a good idea to use a PCIE card or not, but that's just a personal opinion.