Yes - you can apply outland while visiting Canada. My husband was here in Canada for the entire time his application was being processed. If you apply outland, make sure you indicated your address in Canada as your mailing address to make sure that all correspondence is sent to you here.
Outland is usually faster than inland but not always (nothing is ever guaranteed). If you are from the US or UK or another country with fast outland processing times - then definitely apply outland.
Keep in mind that if you are asked to attend an interview and you apply outland, that interview will be held in your home country (not in Canada).
Also, you should make sure you maintain valid status in Canada as a visitor by applying for extensions, etc. until your PR is approved.