I disagree with (1) and (3). I think for a novice bending low notes is more difficult. For me the easiest note to bend was hole 6 on a C harmonica. Also, I don't think wood vs plastic matters for how easy bending is.
The reason that wooden combs are harder is because the wooden comb swells from moisture (e.g. your saliva) and creates micro-gaps which subsequently requires increased draw or push force from the end user to perform the bend.
They sound the best though!