I have no context to judge the loudness of the Cobras on a VStar, nor do I know what its like for noise ordinances in Canada. But I can add value based on what I know on the Roadliner/Stratoliner models.
1. Noises ordinances from what I have seen in Colorado are not enforced. Many of us have pipes that louder than what the stock pipe is, and as long as you are not the idiot that goes blaring through a residential neighborhood, the police never look at you twice. I suppose if they wanted to pull you over for suspicion of something else, this would be as good of an excuse as any. I have never been harassed about my pipes by law enforcement.
2. The Cobra pipes on a *liner sound awesome! However as previously mentioned, there is a point of being obnoxious, and after spending a few days riding behind someone with those pipes, they are right at that line. Many people in the group did not want to ride behind this guy because his pipes were too loud. I run a Vance and Hines Exhaust, and while their sound is not for everyone, they are a nice blend of ear pleasing sound and muffled enough to begin to disappear at highway speed so you can enjoy the ride.
3. Performance. Again, I no little about the VStar bikes, but the *liners have an EXUP valve and when you remove it, you lose performance. Move from a 2 into 1 pipe to duals, you gain sound, but lose more performance. You may need a Power Commander to restore that performance. Its not dramatic, but you can feel the torque loss on the liners. Several friends went to a slip on that allowed them to keep their EXUP valve. Frankly, I think mine looks better, the stock pipes are unattractive to me, BUT, I think their sounds better and I think they did not lose the torque that I lost, and they did not have to add a Power Commander to boot.
Just my .02