You may mail your application to either offices. You may want to check the statistics for processing times for Canadian Visa offices, and submit your papers to the office that processes cases faster.
http://www.cic.gc.ca/english/information/times/international/15-temp-workers.aspThey sometimes require interviews, but as far as I know, they seldomly do it. As long as you have a positive LMO, are healthy and have complete requirements, chances are there wouldn't be problems. Thing is, if they would want to interview you, you need a travel visa to the US.