VOIP down. Data up. Initial look doesn't reveal anything obvious. No redundancy. Reload equipment or keep data up while isolating the problem? Why or why not?

I'm thinking more on the side of branch offices where we don't have high availability equipment. Our job is all about uptime. But sometimes power cycling a couple of suspect devices is faster than finding the exact problem. Would you take down another service in hopes to fix another one more quickly?

edit: what if it were data down and VOIP up?