How can I reliably move photos from an iPhone and iPad to a Mac without losses or duplicates?
As an alternative to PhotoStream, I use PhotoSync to reliably move photos to my Mac without losses.  This is via wifi from PhotoSync on the iPad to the PhotoSync Companion on the Mac.  You will then need to import those photos into iPhoto on the Mac.

Without duplicates is bit harder.  PhotoSync will synchronise your photos without considering what you may have transferred using other methods (e.g. PhotoStream and iCloud).  So you will need to find duplicates yourself - either don't transfer those you already have in Mac iPhoto, or transfer the lot and sort out later on your Mac.

Regarding a precise workflow, I suggest you play around with PhotoSync and then you will quickly develop a workflow which suits you.