user vs utilizer

user and utilizer both are nouns.

Word	Noun	Adjective	Verb	Adverb
user	Yes	No	No	No
utilizer	Yes	No	No	No

As nouns, utilizer is a hyponym of user; that is, utilizer is a word with a more specific, narrower meaning than user:

user: a person who makes use of a thing; someone who uses or employs something
utilizer: someone who puts to good use

Other hyponyms of user include consumer, end user, usufructuary, utiliser, wearer, tweep.

user (noun)	utilizer (noun)
a person who makes use of a thing; someone who uses or employs something	someone who puts to good use
a person who uses something or someone selfishly or unethically
a person who takes drugs