1st stage Hose protectors - necessary?

It makes the hose lighter and easier to roll into a loop for storage. Answer: No Benefit for me.

I have used braided hoses on my primary second stage and I think the flexibility translates to some degree of comfort,

 

Almost never. Are you a sea lion?

I've dived with both rubber and braided on a clipped off SPG. No noticeable difference in the water. Rubber is a few ounces heavier and doesn't wrap quite as nicely in the bag, but those are minor details.

Dupont makes a thin Kevlar reinforced HP hose with a smooth outer layer if you want the luxury option.