As adjectives the difference between peakier and peaker
is that peakier is comparative of peaky while peaker is which peaks, reaches or forms a peak.
As a noun peaker is
one which reaches or forms a peak.
peakier
English
Adjective
(head)
(peaky)
peaky
English
Adjective
(er)
Sickly; peaked.
Characterised by peaks.
peaker
English
Noun
(
en noun)
One which reaches or forms a peak
Adjective
(
en adjective)
which peaks, reaches or forms a peak