As nouns the difference between avantgarde and unconventional
is that avantgarde is while unconventional is something or someone that is unconventional.
As an adjective unconventional is
not adhering to convention or accepted standards.
unconventional
English
Adjective
(
en adjective)
Not adhering to convention or accepted standards
Out of the ordinary
Atypical
Noun
(
en noun)
Something or someone that is unconventional.