I go a lot quicker up hills this year having lost a bit of weight. It is really noticeable for me, it makes riding a lot more enjoyable!
However… my bike this year is the lightest I've ever had, I like it more than all the others. Heavier bikes don't ride as nicely IMO. If I wasn't racing I'd have something with more travel and wider tyres, but would still make it as light as practically possible.
I am amused by how many people on Weight Weenies riding 17lb hardtails are 90kg+ though.
Rockhopper won't be any tougher than the Stumpy either, as has been observed, carbon bars are likely stronger than alu ones, I'd trust F90s over Toras too.