How would you rate Windows 95 vs. Windows 98?
The fact you're considering 1.2.0.0 rev2 indicates your OS is at least Windows 7 (Java 9 is not compatible with XP) and very likely a 64-bit edition (Java 9 never received an official x86 release, only a "forgotten" one which Oracle DMCAed wherever they found it), which is good enough for the latest version of the mod.
Azureus/Vuze/BiglyBT was never known for its low resource consumption, but "not low" doesn't mean "unusably high", and there are tweaks to keep things under control. Deliberately running old versions will have very little impact on this and is not worth the loss of functionality and security.