• d.pop(key) -- consider using this if you need the value for the item being deleted, and/or you want to specify a default value and don't want an exception raised if the key doesn't exist.
  e.g., value = d.pop(key, None)
• del key -- consider using this if you are certain that the key exists (or you expect an exception if it doesn't), and you don't need the value of the item being deleted.
  e.g., del key

From the official Python language documentation:

del d[key] Remove d[key] from d. Raises a KeyError if key is not in the map.

pop(key[, default]) If key is in the dictionary, remove it and return its value, else return default. If default is not given and key is not in the dictionary, a KeyError is raised.

https://docs.python.org/3/library/stdtypes.html#mapping-types-dict

I would not worry about the performance differences unless you have specific reason to believe that they are causing meaningful slowdowns in your program, which is unlikely.

The real reason you might choose to use del vs pop is because they have different behaviors. pop returns the value for the popped key, so you would use pop if you want to do something with that value at the same time as you remove it. If you don't need to do anything with the value, but just want to remove the item, use del.