What would your objective be?
If you need additional storage, by all means, buy a m.2 pcie ssd.
The cost per gb is comparable to a conventional 2.5" sata ssd.
A m.2 pcie ssd will be faster in sequential benchmarks.
But the reality is that you would not really notice the difference.
Most of what we do is small random i/o and sata or pcie devices differ little in such performance.
I can't tell the difference personally except when copying large files. My two cents would be 1TB isn't much storage these days, you might as well have more if you can afford it, and if he's buying another drive there's not much reason not to get NVME.