I have both the PO 7 and the PO 9. I have carried both. I had a Vortex Viper RDS installed on the PO 9 by primary machines, they also cerakoted the slide titanium. I've been carrying the po9 with the RDS for about a year-and-a-half now, it may be a little heavy for some but I don't mind this darn thing shoots better than I do. Also I carry an extra magazine which gives me a total of 39 rounds, that's a huge Plus.
IMHO P-09 is better than the PO 7