i think it depends on how important it is right now in your life to start laying down roots with your bf. if what you are doing now works for you and you can wait more than a year, then go for commonlaw. If you want to make a change sooner, then get married. We applied in march, transfered to the visa office in may, and just got a request from them yesterday. So Ottawa is processing a bit quicker right now. Current applicants are landing in 5-6 months!
A civil ceremony is perfectly acceptable. CIC isn't looking for how much you spent. They are looking for legitimacy, So invite family and close friends. Our ceremony had 22 guests, and a lovely dinner afterwards. I didn't break the bank on budget, though i did allow myself a little glamour and glitz.
Since you have been in an ongoing relationship for 7 years, my guess is you'll be able to prove your relationship is real and ongoing, and that it is known to your family/friends. I think what it really comes down to is how long are you ok with waiting to legally live/work in canada?