I'm not sure what year my helmet is from, but I'm guessing maybe 5, 6, 7 years ago, and the big improvement to my old helmet similar to your 97 one is the remarkable airflow increase. Lighter too , but the air flow is a big priority for me, and there are lots of mid range priced ones in the 50 to 80 90 that have just as good vents/airflow. It's much hotter and more humid here in Montreal, so these aspects are very much appreciated.
Yep, I like my old Bell for sentimental reasons and the fact that it is bomb proof (dropped so many times without a crack in the hard shell) but my newer helmet is about half as light and feels like it's not even there.