I haven't read the 4 pages but of your choices the standout picks are the Shield and the G43. In terms of reliability and track record, both of those stand out against the ruger and especially the cw9. The shield is perhaps the best selling single stack of all time. The Walther PPS M2 is nice but aftermarket support is minimal and it is as heavy as a G26 - and most people buy single stacks for both their lighter weight and slimmer design.Was looking at the Ruger LC9s, Glock 43, S&W Shield, Walther PPS M2, Kahr CW9.
The Glock 43 is the the smallest, lightest weight, most reliable of your options and if specs on paper are the most important, it's your choice. That being said, I found the Shield to have less recoil because of the larger grip front to aft which gave me more room for my support hand to get traction for recoil control. It is also equally reliable. I solved this problem with a Hogue grip sleeve on the g43 which worked wonders. Also, with tango down g43 mag extensions (and springs) you have the most flexible package available - a super light and small (6 round mag) gun or an 8 round gun if your wardrobe allows.