P3 is a reasonable compromise if you want to double your exp gain and increase rune and other junk drops (charms, etc.) This assume you kill most/all minions whether on purpose or just due to the spell you use (blizzard is good for this)
Nor is it unreasonable to get enough +skills to make the difference in kill speed between p1 and p3 negligible at best; with blizzard. The biggest thing is a string of missed blizzard shards is more noticeable/significant on p3 than p1.
