I found two entries for Ed/Edward Bunton on FindMyPast. The first one was for the Pretorian which departed Glasgow on 5 July 1921 for Montreal. The entry is for Edward Bunton of 42 College Street, Maxwelltown, Dumfries; age 33; Farm Lab.; landing at Montreal - but his name is crossed off the list.
The second record is for the Melita which left Liverpool on 12 July 1921 also headed for Montreal. He is listed with a group of other passengers under the heading British Government Passengers (I'm not sure if this means it was an assisted passage). He is listed as Ed Bunton, again of 42 College Street, Dumfries, age 33, Farm Hand. The destination is only listed as Canada, no specific province or city.
So it looks like he was booked on the Pretorian but for some reason sailed a week later on the Melita. There are a few records in the Drouin Collection on ancestry for Edward Bunton, Edward Miller Bunton, Albert Edward Bunton....I don't have a sub so I can't tell if these fit with the birthdate you provided. But perhaps someone else with a sub can do a lookup.
Looking at your photo, I can tell you he definitely did not emigrate to British Columbia! We don't get that much snow - only sun, sun, sun. Okay and a bit of rain now and then.

Hope this helps,
Lynwen