I would say the my highest recommendation IS for Landsharkz; to be fair I've not "tried many others" but frankly, I've never wanted to! There are obviously other great suppliers, but for selection and customer satisfaction *in my opinion*.... Landsharkz. Even going to the website is easy!
Not only have I only ever received impeccably minted geocoins, they have a large amount of Canadiana designs to chose from (which may be relevant seeing as you are asking about Canadian suppliers).
Landsharkz also design and manufacture their own products; they aren't simply a "packager-and-sender". Their website has very clear pictures of their work - just take a look at their gallery and see how many geocoins they make for other people (the ones that say "Only Available From...."). If folks in the UK are getting Landsharkz to do their geocoins... it's pretty clear they are doing something well!!!!!!
If you are looking for geocoins to release "into the wild" then you have the option to buy smaller geocoins in "multiples" and save a few dollars. I was thrilled to be so welcomed when I made appointment to visit "Chez Landsharkz" when I was in Victoria.
I have purchased geocoins "over the border" and I've not been "hugely dissatisfied" with that approach yet (other than the mystery charges that sometimes arrive with US sourced items) .. but I've been MORE than satisfied with Landsharkz. I am not un-recommending others (I've bought some TB's from CachersToyBox in Ontario also and I've heard great things about 3geeks!) but that's where I'd start!