Hi
Get both of them. You never know if the first one is delayed or not approved. You may also have two jobs, if you can get to both. Full time is considered 37 hours a week but I know many people who work two jobs. Of course, both places have to be relatively close.
If you are outside Canada, Just apply for your first work permit and then come here and apply for the second one here if you wish. You may take your time to do so, as long as you're here then you can look at options.
1 job, CIC will not issue 2 work permits for different jobs to the same applicant.
PMM