Even if you are a Canadian company, unless your business strictly deals with all things Canadian and that is your identity, then I would go for the ".com" approach. It is still the suffix most people automatically type and first and foremost, you want clients and potential clients to find you.
There are additional options whereby you can register both and then just have the ".ca" point to the ".com" site, or vice versa. That way you would cover most possibilities. With a myriad of additional suffixes added in the last few years, it is more and more confusing for people searching to know whether or not they have the right company. The ".com" is the easiest one to use, I believe.
When I see the ".org" or the ".net" suffix, I think of a smaller group or company, perhaps a charitable institution. The ".edu" represents an educational institution and well, you can guess what ".tv" is for. The fact is, there are so many additional suffixes that it is hard to keep up and I for one am not really interested in doing so. I have my ".com", that is the one most people assume I use and that in itself speaks volumes.
If, however, you want to use a different suffix for your web address, then you need to promote, promote, promote and make sure that whatever your choice, it is firmly fixed in people's minds. You want them to find you. Make it as easy and logical as possible.