Extractions are preferred when more significant profile (lips) changes are desired.
IPR can retract the upper incisors by realistically 1-2mm at the most.
Extraction of 2 premolars can give on average 14mm of space to relieve crowding and reduce incisor protrusion.
However, the exact amount of upper lip retraction is not a 1:1 correlation with the amount of incisor retraction.