The EZ is indeed bigger than the Shield. In fact, the EZ has very little in common with the standard Shield, other than both being plastic modified Browning style handguns produced by S&W. Most of the size difference is the 1/2" longer barrel and 1/8" wider slide.
It may be though that S&W has found the best solution so far for arthritic hands. Besides the easier slide manipulation, it's also much easier to disassemble and clean. As much as I like my Kahrs, you gotta hand it to S&W for innovation.