A better gauge of hand feel will be percentage thicker; not simply the number in mm. The RAZR Maxx is around 25% thicker at its thinnest than the RAZR. It's still a very thin phone, but the difference is noticeable and significant, from a design standpoint. The RAZR's thinness is revolutionary for this market, though, so even though the Maxx is 25% thicker it's still thinner than almost all other comers (iPhone 4S, GNex, Rezound, etc.); good job, Motorola!
Whether it matters to you or not depends on whether you need ultra-svelte or pretty-svelte-with-awesome-battery. I'm fine on battery on my OG RAZR and I love the feel of it, but if you even have a passing thought that you'll maybe want more battery the Maxx is a pretty easy choice.