No reason you can't use both.
I have 2 instances of p2pool running on 2 different machines with a PPS pool as a backup
cgminer makes it easy to maintain 100% uptime even when making upgrades.
{
"pools" : [
	{
		"url" : "192.168.0.129:9332",      <- dedicated p2pool machine
		"user" : "WaterOne/1000+1",
		"pass" : "pass"
	},
	{
		"url" : "192.168.0.181:9332",      <- my workstation which is always on
		"user" : "WaterOne/1000+1",
		"pass" : "pass"
	},
	{
		"url" : "backup-pool:port",  
		"user" : "backup-user",
		"pass" : "backup-pass"
	}
],