Your P30 is still largely based on the USP that was designed 30 years ago, isn't it? Unlike the VPs, the .40s weigh the same as the 9. So either way I assume they were .40s first and foremost (or at least designed to accommodate the .40) which is probably part of the reason why they're thicker.
I wonder how an analogy to the F-117 and F-22 works. The former being a product of the limited modeling ability of computers available at the time.
The 365 is probably closer to what a modern 9mm "should" be in terms of shedding extraneous weight. Without commenting on shootability... just function and lifespan. Another few decades of more data and better modeling will usually produce a more streamlined design.