performance tests / cube with rounded corners (openSCAD)

I did some performance tests on different functions, which all produce a box with rounded corners. You can find them in the scad-file.

Here are my results:
PreView Render STL-Size
v1 1 seconds 0 seconds 5.911.647
v2 0 seconds 215 seconds 3.773.709
v3 1 seconds 0 seconds 2.053.339
v3a 121 seconds 0 seconds 2.053.339
rB 0 seconds 171 seconds 3.648.521
rc 126 seconds 0 seconds 2.057.417

v1 looks good in terms of speed ... but leaves a 5MB file.
v3 has the same speed and the file size is the smallest.
All other versions have bad run times either during preview or later when rendering.
Very interesting is the very significant runtime difference between v3 and v3a.

So...the winner is this one:
module BoxMitAbgerundetenEcken3(x, y, z, r=1) {
hull() {
translate([ r, r, r]) sphere(r=r);
translate([x-