Broadly and generically speaking, doubling the number of drivers should result in a 3dB increase in volume, but it would depend on what 410 cab and what 210 cab you're talking about. Is ANY old 410 louder than ANY 210? Maybe not; I think there are probably good 210s that outperform mediocre 410s, but -- again, generally speaking -- a 410 should be louder than a comparable 210 cab. Whether this translates to more 'punch' is subjective, and it doesn't necessarily result in better 'low end clarity' either. It's highly dependent on which cabs you're talking about.
Also, switching from an 8Ω cab to a 4Ω cab would result in your amplifier producing more power, presuming you have a solid-state amp and that it will safely drive a 4Ω load, which virtually all of them do. This would also result in more volume, but again, not necessarily more 'punch' or more low-end clarity.
Personally, I kinda hate the 410 form factor generally and would much rather have two (matching) 210s for the modularity it offers.