Bladepitch .....
Don't think Lu will be able to help you with this!
Where to start ....
1. 500 less maintenance intensive then the 300.
2. 500 M/R Blades easier to Remove/Refit when required.
3. 500 has Pop-Out float kit available .... Fixed floats on 300 & 500 are a pain to maintain aboard a ship.
4. Yes 500 much less prone to Ground Resonance then 300 though i understand 300 with Elastomeric lead/lag dampers are now much better.
5. 500 much better control response and more agile ... which makes deck landing in rough conditions much safer.
6. Tie down provisions on the 500 way better than the 300.
There is probably more ... but my head hurts ... time for a lie down!