Is rhotic or non-rhotic more common?

<<A frequent example in present-day Standard English is the omission of two [r] sounds from words like "caterpillar, Canterbury, reservoir, terrestrial, southerner, barbiturate, governor and surprised." >>

Do we really? Let's see -- I would say those words as follows:

caterpillar - caddapiller - drop 1 R, change T to D
Canterbury- Cannerberry - drop no Rs, drop T
reservoir - rezavwar - drop 1 R
terrestrial - ter-res-chreeul -- drop no Rs
southerner- sutherner -- drop no Rs
barbiturate -barbitcheret -- drop no Rs
governor - guverner -- drop no Rs
surprised- suhprized -- drop 1 R

But that's probably because I'm rhotic to begin with, and we rarely drop final Rs.

This is how I would say those words -I have a General Australian accent.

caterpilar - cata or cadapilla (drop 2 r's, i'm not consistent with t/d, i use both)
Canterbury - cantabury - drop 1 R, keep the T
Reservoir - rezavwah - drop 2 r's
Southerner - suthena - drop 2 r's
Barbiturate - Bahbiturate -drop 1 r
Govenor - guvanah - drop 2 rs
Surprised - suhprized - drop 1 r

@Trimac20: Well it isn't relevant for you, because you're totally non-rhotic. ;)