Phone call is generally considered the quickest method by most folks who have changed an address.
The newer webform has a specific option to change address (similar to ecas) but no one knows if it's more efficient than the current webform or ecas. I'd think even with the new webform, a human operator is still checking the request and updating it manually which means it will be delayed.
This is the new webform link:
https://www.cic.gc.ca/english/contacts/web-form.asp?v2
What stage are you in? Especially if you're done with testing or close, it's important to update the address asap since changing the address close to oath has caused issues with citizenship certificate mailing for several folks. In that case, a phone call would be the best option.