Is it a good practice to delete all the IPS 3.4.7 files except conf_global.php and uploads folder, before extracting IPS4 files and running the upgrade ?

I usually just overwrite the old 3.4.7 files with the new files. Has worked just fine so far!

I usually just overwrite the old 3.4.7 files with the new files. Has worked just fine so far!

​Well removing old files which are not in use anymore is good. I over write on point releases and upon major releases like 2.x to 3.x and from 3.x to 4.x, I prefer clean up.  In case of trojan attack or virus issues it becomes easier to compare what's wrong. 

​Well removing old files which are not in use anymore is good. I over write on point releases and upon major releases like 2.x to 3.x and from 3.x to 4.x, I prefer clean up.  In case of trojan attack or virus issues it becomes easier to compare what's wrong. 

​That's a good point. I might try doing exactly that when I upgrade next time.

Thanks for the feedback I deleted all IPB 3.4.7 files except :

Uploads

Public

Conf_global.php

Everything went well with the upgrade !