Never used Mr Hobby's primer.
I guess it depends on how thick you put it on and how much white you need. I use Tamiya White on Gundams (which are pretty much white anyway)
or anythign that needs a cover-up of all the crappy sanding I do (eg clean, polished smooth surfaces)
. For darker colors I'd either hit it with the rougher grey primer or even just straight on with the paint. Basically, I'd only use White Primer if I really, REALLY need a white base--again, that means Lily-white Gundams.
In essence (And this is IMHO)
you'd only use white primer if it needs to be white or it requires a light base (in other words you're painting colors like orange, yellow--those bright translucent ones that look terrible if you're painting on gray or other undercolor)
. If you use fatigue greens/camo/black, and other 'naturally opaque' colors, primer's next to unnecessary.
...oh, and a delayed reaction to the pics: "The Guuuuuncannon of the Opera is heeereee---inside my mind~~~~"