Immediate thoughts from today:
I ran the old set most of the day. I started with the old and ran it through a couple of drills and then switched. The sound on the new set was noticeably different, and it cut out at what I think are lower surrounding volumes than the old set. The volume levels don't seem like they match between the sets, and There are some differences in the frequency response between the two sets. I noticed that certain frequencies sounded louder or softer between the two sets, and I refer the older version's frequency response, I think.
More to come, but there is definitely a noticeable difference in the older and newer TCI DEHP units. I'm going to try to find some MSA units and some Peltor units to compare against the TCI product in the near future.