A single profile tells you where the time goes and leaves the question of whether that is unusual. A comparison between two profiles answers the question you actually have: what changed.
blackfire run php bin/export.php # reference
# ... change something ...
blackfire run --reference=41 php bin/export.php
# and in CI, as a gate rather than a report
# .blackfire.yml
# tests:
# "Product page stays under budget":
# path: "/products/.*"
# assertions:
# - "metrics.sql.queries.count < 10"
# - "main.peak_memory < 20M"The assertions are the part worth setting up, because they turn performance from something noticed after a release into something that fails a build. A query-count assertion catches the N+1 a new eager-load omission introduces, which is otherwise invisible until the data grows. The overhead is low enough to profile production traffic occasionally, which Xdebug is not.