The most important one may be the
improved steering nozzle that eliminates the 'dead zones' to either side of center which makes for jumpy (seems like 'sensitive') steering.
Then (in order of importance - or what usually breaks first) would come the
grease port mod, the stuffing tube support elimination and the easier battery containment mod. Be aware the stuffing tube support mod (puts a bearing at the stator end) will slow the boat down some, but it will be rock solid and no spider bracket to fail (requiring a jet drive replacement)
Then Pilot Johns beautiful
intake grate and maybe the
Reverse bucket option which replaces the nozzle trim (which is really of limited use).