Applying through Vegreville requires the following to be eligible:
http://www.cic.gc.ca/english/work/apply-who-eligible.asp#inside
Eligibility to apply from inside Canada
You can only apply for a work permit from inside Canada if:
you have a valid study or work permit, or your spouse or parents have a study or work permit
you have a work permit for one job but want to apply for a work permit for a different job
you have a temporary resident permit that is valid for six months or more or
you are in Canada because you have already applied for permanent residence from inside Canada. You will have to pass certain stages in the main application process before you can be eligible for a work permit.
So if none of these apply then application must be made from outside Canada. Flagpoling means seeking entry: you actually depart Canada and seek to re-enter. If the work permit applied for at the Port of Entry in this process is refused, visitor status that was previously valid is gone and is also being asked for again and could also be refused.
Lots to think about to decide which way will be best in the particular circumstances.