I have Pierce +0 extensions on 2 mags and factory floor plates on 2. I don't notice a difference in performance, but it is more comfortable to shoot. They make the mags a bit more difficult to carry (conceal) thanks to the added girth at the bottom. I think I'd consider using a G23 mag before I added the extensions.
Heads up--don't buy the extensions that add capacity. They are known to pop off if you mishandle the mag (personal experience), and with the smaller GLOCKs they have been known to cause feed issues. For this reason I went to the +0 extensions and they have worked well.