upgrade vs prefer

upgrade is a noun but prefer is not a noun.

Word	Noun	Adjective	Verb	Adverb
upgrade	Yes	No	Yes	No
prefer	No	No	Yes	No

As verbs, prefer is a hyponym of upgrade; that is, prefer is a word with a more specific, narrower meaning than upgrade:

Other hyponyms of upgrade include tenure, bring up, spot promote, ennoble, entitle, gentle, favor, favour, brevet.

upgrade (noun)	prefer (noun)
the act of improving something (especially machinery) by raising it to a higher grade (as by adding or replacing components)
hardware that provides better performance than an earlier version did
the property possessed by a slope or surface that rises
a reservation that is improved
software that provides better performance than an earlier version did
an upward slope or grade (as in a road)

upgrade (verb)	prefer (verb)
to improve what was old or outdated	select as an alternative over another
give better travel conditions to	like better; value more highly
get better travel conditions	promote over another
rate higher; raise in value or esteem	give preference to one creditor over another
give a promotion to or assign to a higher position