I went from P3P to P4P at start of this year. Yes, images are a bit better so can get slightly higher res orthophotos if flying at same altitude. A big plus is the longer range batteries on the P4P- I generally aim for about 18-20 minute flights (gets me to 30% battery when alarm kicks in. With P3P I was usually only getting 13-15mins.
Only downside I can think of is the cost to upgrade.