I assume you refer to Forger Classic as the old one and Forger 2024 as the new one.
I would focus on the Forger 2024 version, as the features have improved and optimized for newer OS versions and CPUs inside the iPad. When you have explored the Classic, you might find here a nice list of the new features:
The ZRemesher (coming from ZBrush) is typically already worth the upgrade.
The Classic version is no longer available, except if you had the license, then follow this article: (As I write in a forum, that might be of interest to some)
The FAQ about Forger, related to common tech support questions, is perhaps worth a shot.