Debugs will always impact CPU utilization because not only does the processor have to do it's work, with the debug running, it then has to tell somebody about it doing it's work. The debugs were designed to be as unintrusive as possible, and for the most part, it's safe to run a couple without serious degradation of performance.
Use of a syslog server can mean double work if logging console isn't disabled. In that situation, not only would the debugs be sent to the syslog server (more IP process), they would also be sent out the console port where they normally go, too.
