Boolians aint good when your learning modeling and you want to try to keep it nice and clean, when your starting off there more hassle than good.

Once you get going and know what they do they do have their place in the toolset, I use them for short cuts but I make sure that I know what they are going to do and how to sort out the topology after using them, to make it nice and clean.

Stick to learning to model manually, its boring but you get to know what the individual edges and smoothing does.

I wouldent use them for a deformable object, that would be asking for trouble, unless you cleaned it up.

Render ing with MR and boolians may be that you converted to sub-d's without it being 100% Quad mesh (as MR used to fall over when there was an ngon or a tri using sub-d's).