I don't know anything about Petcam-couldn't you ask your vet about it though?
I have been using Metacam for my dog for 1yr and 4 months, intermittenly, and haven't had issues. As said, all drugs have possible side effects. Since you're not having problems with that one and it works, I see no reason to change.
Your vet is probably the best person to ask about the Petcam though. But with little dogs a 100mL bottle must go a long way at least.