in Australia we mainly use 3.5" rubbers on our booms (except our 50mtr - thats always 4" unless doing columns) when off the stick. i've been searching the net and noticed that other countries use like china 5" rubbers straight off the 5" bend. we really only use 4" rubbers for our other machines when pouring a big slab. personally i love the 4" drop hose - i find it easier when operating and working on the hose.

Here in Norway we use 5.5" and 4.5" mostly.
We usually reduce down to 3" on walls and stuff like that.