Just whatever you pistols like. I know I did a bunch of research before I bought one. Most the research I found was folks weren't having good luck with lead in Walther PPS 9mm, but most were using a RN. So I chose the Lee 120gr TC (have 2-cav and 6-cav), which drop around 123-124gr. They run flawless in my Walther using a minimum charge of Titegroup.
Be sure to slug your barrel. I run these 120gr TC in my PPS and PK380. The .380 I size to .356, but my 9mm I have to size at .357.
Between sizing and using a product called PB Blocker, it takes a lot of rounds before I need to clean my barrels.