Hi Donnie, basically, the Shield Plus is not an easy racking gun like the EZ models. The Performance Center models have upgraded parts, including night sights and ported barrel & slide. You can compare all the differences yourself on the S&W web site.
smith-wesson.com/

Hi Donnie and welcome back. The EZ models have specifically calibrated recoil springs for easier racking/magazine loading than the standard Shield models. There is a higher capacity double stack EZ model called the Equalizer as well and give more rounds than the single stack EZ models. Cheers, stay safe and enjoy!