Which do you use? Perfmon CPU counter, or system.cpu.util

[BrentN]

Zabbix 1.8.10 (appliance)

I set up a host to collect CPU % utilization using both the perfmon counter and Zabbix agent methods.

perf_counter[\Processor(_Total)\% Processor Time]

and

system.cpu.util[,system,]

I'm getting different numbers (up to 20% difference) for each of these and honestly, I'm not really sure which one to trust as correct. I'm just looking for a little reality check here as to whether or not this is expected. Also, which method do some of you typically use?

Thanks!