I've also been looking at these two phones for a contract 'upgrade' - I'm still very happy with the Nexus 5X I bought myself, so just want to use the upgrade to get my mom a new phone (She has another cheapie Samsung with just 8GB memory, mandatory OS/app updates made the available space virtually nothing).
While I actually like the Huawei's fingerprint reader (use it on my own phone and the ability to swipe from there instead of the screen is something I really want as well), the rest of the phone also looks great for the price
Due to the fact that the Samsung only has 16GB memory makes it a definite NOPE - that amount of memory simply won't be enough in the next 2 years. Even if you'd only install a few apps(eg. Whatsapp and Facebook Lite), every time it(or any of the Google services) updates, you'll have less memory and eventually run into problems where the apps can't update because there's not enough space to download the new versions. You could go on with the older versions of the apps for a while, but eventually they disable the old version completely.
The fact that the old Samsung had several pre-installed apps that were not removable(You could only 'disable' it, causing it to uninstall updates and revert to the originally installed version) also doesn't help much (Apparently Huawei has a few pre-installed as well but they can be removed without issue)
Edit: According to spec sheets from the manufacturers, available space on both phones are as follows. Not including external SD card support as some apps still cannot be installed on there:
Galaxy J5 Pro: 16GB - Available 10.1GB
P10 Lite: 32GB - Available 22GB
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